workflows: condition steps with secrets on pull_request_target event

In a pull_request event, vars are available, but secrets are not. Thus
the steps will run, even though there is no secret to request those
tokens - they will fail.

The intent was, to skip them entirely in that case.

(cherry picked from commit 50f6d8d909)

.github/workflows/codeowners-v2.yml

@@ -67,7 +67,7 @@ jobs:
         run: nix-build trusted/ci -A codeownersValidator
 
       - uses: actions/create-github-app-token@df432ceedc7162793a195dd1713ff69aefc7379e # v2.0.6
-        if: vars.OWNER_RO_APP_ID
+        if: github.event_name == 'pull_request_target' && vars.OWNER_RO_APP_ID
         id: app-token
         with:
           app-id: ${{ vars.OWNER_RO_APP_ID }}
@@ -103,7 +103,7 @@ jobs:
         run: nix-build trusted/ci -A requestReviews
 
       - uses: actions/create-github-app-token@df432ceedc7162793a195dd1713ff69aefc7379e # v2.0.6
-        if: vars.OWNER_APP_ID
+        if: github.event_name == 'pull_request_target' && vars.OWNER_APP_ID
         id: app-token
         with:
           app-id: ${{ vars.OWNER_APP_ID }}

.github/workflows/reviewers.yml

@@ -44,7 +44,7 @@ jobs:
       # See ./codeowners-v2.yml, reuse the same App because we need the same permissions
       # Can't use the token received from permissions above, because it can't get enough permissions
       - uses: actions/create-github-app-token@df432ceedc7162793a195dd1713ff69aefc7379e # v2.0.6
-        if: vars.OWNER_APP_ID
+        if: github.event_name == 'pull_request_target' && vars.OWNER_APP_ID
         id: app-token
         with:
           app-id: ${{ vars.OWNER_APP_ID }}