test: Change the installer for setup-matrix-synapse.

There is a bug in Synapse and changing the installer seems to fix the
problem.

.github/workflows/ci.yml

@@ -411,6 +411,7 @@ jobs:
 
       - uses: michaelkaye/setup-matrix-synapse@main
         with:
+          installer: poetry
           uploadLogs: true
           httpPort: 8228
           disableRateLimiting: true

.github/workflows/coverage.yml

@@ -48,8 +48,9 @@ jobs:
       with:
         python-version: 3.8
 
-    - uses: gnunicorn/setup-matrix-synapse@main
+    - uses: michaelkaye/setup-matrix-synapse@main
       with:
+        installer: poetry
         uploadLogs: true
         httpPort: 8228
         disableRateLimiting: true