.github: update tibdex/github-app-token to release v1.8.0 (#7495)

The main motivation for this change is to stop using the deprecated
set-output function which triggers deprecation warnings in the action.

Change-Id: I80496c44ea1166b9c40d5cd9e450129778ad4aaf
Signed-off-by: M. J. Fromberger <fromberger@tailscale.com>

.github/workflows/go-licenses.yml

@@ -42,7 +42,7 @@ jobs:
           go-licenses report tailscale.com/cmd/tailscale tailscale.com/cmd/tailscaled > licenses/tailscale.md --template .github/licenses.tmpl
 
       - name: Get access token
-        uses: tibdex/github-app-token@f717b5ecd4534d3c4df4ce9b5c1c2214f0f7cd06 # v1.6.0
+        uses: tibdex/github-app-token@b62528385c34dbc9f38e5f4225ac829252d1ea92 # v1.8.0
         id: generate-token
         with:
           app_id: ${{ secrets.LICENSING_APP_ID }}

.github/workflows/update-flake.yml

@@ -27,7 +27,7 @@ jobs:
         run: ./update-flake.sh
 
       - name: Get access token
-        uses: tibdex/github-app-token@f717b5ecd4534d3c4df4ce9b5c1c2214f0f7cd06 # v1.6.0
+        uses: tibdex/github-app-token@b62528385c34dbc9f38e5f4225ac829252d1ea92 # v1.8.0
         id: generate-token
         with:
           app_id: ${{ secrets.LICENSING_APP_ID }}