actions: Workaround YAML limitation for timeout-minutes

Because Github Actions wants an int, we use fromJSON to hack around
this.

.github/workflows/release.yml

@@ -46,7 +46,7 @@ jobs:
   release:
     name: Release ${{ matrix.OS_NAME }}
     runs-on: ${{ matrix.os }}
-    timeout-minutes: ${{ vars.JOB_TIMEOUT }}
+    timeout-minutes: ${{ fromJSON(vars.JOB_TIMEOUT) }}
     strategy:
       matrix:
         os: [ ubuntu-latest, windows-latest ]
@@ -144,7 +144,7 @@ jobs:
   macos_release:
     name: Release MacOS universal
     runs-on: ubuntu-latest
-    timeout-minutes: ${{ vars.JOB_TIMEOUT }}
+    timeout-minutes: ${{ fromJSON(vars.JOB_TIMEOUT) }}
     steps:
       - uses: actions/checkout@v3