matrixsynapse: Allow installing new dependencies

Fixes: #2556

Should be merged after fix for https://bugs.debian.org/1122841 is in unstable.

- This fixes issue with Matrix Synapse app not being installable from current
unstable.

- matrix-synapse package depends on older version of python3-typing-extensions.
This causes the daemon to fail during startup when older version is installed.
This was reported as https://bugs.debian.org/1122841. After this bug is fixed
and a newer version of matrix-synapse is uploaded, the patch will work as
expected. An alternative was to allow unattended-upgrades to upgrade
python3-typing-extensions from unstable, but has to be done very carefully and
with a lot of testing.

Tests:

- Install Matrix Synapse apps works. This request installation of the latest
version python3-typing-extensions from unstable. The daemon is running properly
after installation.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

plinth/modules/upgrades/__init__.py

@@ -55,7 +55,7 @@ class UpgradesApp(app_module.App):
 
     app_id = 'upgrades'
 
-    _version = 21
+    _version = 22
 
     can_be_disabled = False
 

plinth/modules/upgrades/privileged.py

@@ -75,6 +75,16 @@ Package: python3-pympler
 Pin: release n=sid
 Pin-Priority: 200
 
+Explanation: matrix-synapse depends on python3-rpds-py (>= 0.25.0)
+Package: python3-rpds-py
+Pin: release n=sid
+Pin-Priority: 500
+
+Explanation: matrix-synapse depends on typing-extensions (>=4.14.1)
+Package: python3-typing-extensions
+Pin: release n=sid
+Pin-Priority: 500
+
 Explanation: Make janus package and its dependencies installable from Debian
 Explanation: 'unstable' distribution.
 Package: janus