chore(linux): rename "Debian packaging" to "Ubuntu packaging"

So far the GHA was called "Ubuntu packaging" but the status reported as
"Debian packaging" which was confusing. This change now uses "Ubuntu
packaging" in both places.

We still keep the filename `deb-packaging.yml` because we're packaging
the .deb format, and because it's shorter.

Fixes: #13497

.github/workflows/deb-packaging.README.md

@@ -1,4 +1,4 @@
-# Debian Packaging GitHub Action
+# Ubuntu Packaging GitHub Action
 
 You can manually trigger a deb-packaging action on GitHub, e.g. to test changes:
 

.github/workflows/deb-packaging.yml

@@ -16,7 +16,7 @@ on:
 env:
   COLOR_GREEN: "\e[32m"
   GH_TOKEN: ${{ github.token }}
-  STATUS_CONTEXT: 'Debian Packaging'
+  STATUS_CONTEXT: 'Ubuntu Packaging'
   DEBFULLNAME: 'Keyman GHA packager'
   DEBEMAIL: 'support@keyman.com'
 
@@ -45,7 +45,7 @@ jobs:
           /repos/$GITHUB_REPOSITORY/statuses/${{ github.event.client_payload.buildSha }} \
           -f state='pending' \
           -f target_url="$GITHUB_SERVER_URL/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID" \
-          -f description='Debian packaging started' \
+          -f description='Ubuntu packaging started' \
           -f context="$STATUS_CONTEXT"
 
     - name: Install devscripts