Pin membrowse-action to v1.2.15 in Membrowse workflows

membrowse-action v1.2.16 moved the floating v1 tag to a release whose
action.yml has "${{ github.workspace }}" in an input description. The
runner rejects the github context there, so every Membrowse analyze job
fails in "Set up job" with "Unrecognized named-value: 'github'". The
onboard action has the same problem, and the comment workflow then
fails because no report was uploaded.

Pin the report, onboard and comment workflows to the v1.2.15 commit SHA,
the last release that worked, as the Zephyr workflow already does.

.github/workflows/membrowse-comment.yml

@@ -24,7 +24,9 @@ jobs:
 
       - name: Post Membrowse PR comment
         if: ${{ env.MEMBROWSE_API_KEY != '' }}
-        uses: membrowse/membrowse-action/comment-action@v1
+        # Pinned to a full commit SHA, same rationale as the report
+        # workflow. v1.2.15.
+        uses: membrowse/membrowse-action/comment-action@34719bdb04722be5cbe9c1d6df4a1567ae98238d
         with:
           api_key: ${{ secrets.MEMBROWSE_API_KEY }}
           commit: ${{ github.event.workflow_run.head_sha }}

.github/workflows/membrowse-onboard.yml

@@ -50,7 +50,9 @@ jobs:
           ghcr-debs-tag: ${{ matrix.ghcr_tag }}
 
       - name: Run Membrowse Onboard Action
-        uses: membrowse/membrowse-action/onboard-action@v1
+        # Pinned to a full commit SHA, same rationale as the report
+        # workflow. v1.2.15.
+        uses: membrowse/membrowse-action/onboard-action@34719bdb04722be5cbe9c1d6df4a1567ae98238d
         with:
           target_name: ${{ matrix.target_name }}
           num_commits: ${{ github.event.inputs.num_commits }}

.github/workflows/membrowse-report.yml

@@ -97,7 +97,9 @@ jobs:
 
       - name: Run Membrowse PR Action
         id: analyze
-        uses: membrowse/membrowse-action@v1
+        # Pinned to a full commit SHA so a moved v1 tag cannot break or
+        # swap the action out from under this job. v1.2.15.
+        uses: membrowse/membrowse-action@34719bdb04722be5cbe9c1d6df4a1567ae98238d
         with:
           target_name: ${{ matrix.target_name }}
           elf: ${{ needs.check-changes.outputs.needs_build == 'true' && matrix.elf || '' }}