Release process: make commit message less generic.

We happen to thaw snapshots at different stages than after releasing.

wiki/src/contribute/APT_repository/time-based_snapshots.mdwn

@@ -105,7 +105,7 @@ a specific set of APT repository snapshots must be used:
         git checkout devel && \
         ./auto/scripts/apt-snapshots-serials thaw && \
         git commit \
-            -m "Thaw APT snapshots after Tails $VERSION was released." \
+            -m "Thaw APT snapshots." \
             config/APT_snapshots.d/*/serial
 
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