github: Pin microceph to quincy edge

Signed-off-by: Thomas Parrott <[email protected]>
(cherry picked from commit 9327619)

.github/workflows/tests.yml

@@ -277,7 +277,7 @@ jobs:
             exit 1
           fi
 
-          sudo snap install microceph --edge
+          sudo snap install microceph --channel=quincy/edge
           sudo apt-get install --no-install-recommends -y ceph-common
           sudo microceph cluster bootstrap
           sudo microceph.ceph config set global osd_pool_default_size 1