[snap] chromium won't run over a remote X session

Since upgrading to Ubuntu 20.04.1 LTS from 18.04.5 LTS, starting Chromium Browser over a remote X session fails with
```
peter@fs-peter:~$ chromium-browser
KiTTY X11 proxy: Unsupported authorisation protocol
[28937:28937:1112/080948.455990:ERROR:browser_main_loop.cc(1426)] Unable to open X display.
peter@fs-peter:~$
```

The same happens for apps like `chrome-dominoes` (which, of course, is the critical issue ;) ).

Other applications run over remote X fine (Firefox, Jamulus, several other applications).

Apparently this is not the same as #1897224.
---
ProblemType: Bug
ApportVersion: 2.20.11-0ubuntu27.11
Architecture: amd64
CasperMD5CheckResult: skip
DRM.card0-DP-1:
 enabled: disabled
 dpms: Off
 status: disconnected
 edid-base64:
 modes:
DRM.card0-HDMI-A-1:
 enabled: disabled
 dpms: Off
 status: disconnected
 edid-base64:
 modes:
DRM.card0-HDMI-A-2:
 enabled: disabled
 dpms: Off
 status: disconnected
 edid-base64:
 modes:
DRM.card0-HDMI-A-3:
 enabled: disabled
 dpms: Off
 status: disconnected
 edid-base64:
 modes:
DiskUsage:
 Filesystem Type Size Used Avail Use% Mounted on
 /dev/nvme0n1p1 ext4 229G 36G 181G 17% /
 tmpfs tmpfs 7.7G 16M 7.7G 1% /dev/shm
 /dev/nvme0n1p1 ext4 229G 36G 181G 17% /
DistroRelease: Ubuntu 20.04
InstallationDate: Installed on 2019-11-07 (370 days ago)
InstallationMedia: Kubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
Lsusb:
 Bus 002 Device 002: ID 174c:55aa ASMedia Technology Inc. Name: ASM1051E SATA 6Gb/s bridge, ASM1053E SATA 6Gb/s bridge, ASM1153 SATA 3Gb/s bridge, ASM1153E SATA 6Gb/s bridge
 Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
 Bus 001 Device 002: ID 04f3:0110 Elan Microelectronics Corp.
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Lsusb-t:
 /: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/10p, 5000M
     |__ Port 8: Dev 2, If 0, Class=Mass Storage, Driver=uas, 5000M
 /: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/16p, 480M
     |__ Port 4: Dev 2, If 0, Class=Human Interface Device, Driver=usbhid, 1.5M
     |__ Port 4: Dev 2, If 1, Class=Human Interface Device, Driver=usbhid, 1.5M
MachineType: To Be Filled By O.E.M. To Be Filled By O.E.M.
Package: chromium-browser 1:85.0.4183.83-0ubuntu0.20.04.2
PackageArchitecture: amd64
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.4.0-53-lowlatency root=UUID=bf22c190-dfc3-4cc0-aa69-df0f50d8c822 ro quiet splash vt.handoff=7
ProcVersionSignature: Ubuntu 5.4.0-53.59-lowlatency 5.4.65
Snap.Changes:
 ID Status Spawn Ready Summary
 36 Done 2020-11-11T23:18:24Z 2020-11-11T23:18:35Z Auto-refresh snap "chromium"
Snap.ChromeDriverVersion: ChromeDriver 86.0.4240.193 (4b1dc838fc8d2b55f2147e7a642b20baf443da5c-refs/branch-heads/4240@{#1411})
Snap.ChromiumVersion: Chromium 86.0.4240.193 snap
Tags: focal snap
Uname: Linux 5.4.0-53-lowlatency x86_64
UpgradeStatus: Upgraded to focal on 2020-10-04 (39 days ago)
UserGroups: Jamulus adm audio cdrom dip lpadmin lxd minidlna plugdev sambashare sudo
_MarkForUpload: True
acpidump:
 Error: command ['pkexec', '/usr/share/apport/dump_acpi_tables.py'] failed with exit code 127: polkit-agent-helper-1: error response to PolicyKit daemon: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: No session for cookie
 Error executing command as another user: Not authorized

 This incident has been reported.
dmi.bios.date: 12/18/2018
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P3.30
dmi.board.name: Z370M-ITX/ac
dmi.board.vendor: ASRock
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrP3.30:bd12/18/2018:svnToBeFilledByO.E.M.:pnToBeFilledByO.E.M.:pvrToBeFilledByO.E.M.:rvnASRock:rnZ370M-ITX/ac:rvr:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.family: To Be Filled By O.E.M.
dmi.product.name: To Be Filled By O.E.M.
dmi.product.sku: To Be Filled By O.E.M.
dmi.product.version: To Be Filled By O.E.M.
dmi.sys.vendor: To Be Filled By O.E.M.