ci: raise the viewerjs job budget for the larger browser suite

The cross-browser workflows suite grew from 396 to 496 tests on this
branch, which pushed the whole viewerjs job to about 25.5 minutes
against the 25 minute cap set in #181. Two exact-head runs on this
branch timed out without any test failing: run 39173019283 was killed
on test 474 of 496, and run 39175125474 printed "496 passed (12.8m)"
and was then cancelled during Playwright shutdown.

Raise only the job budget. Browser projects, workers and per-test
timeouts are unchanged. Splitting the browsers into parallel jobs is
tracked separately.

.github/workflows/viewerjs-check.yml

@@ -13,7 +13,7 @@ permissions:
 jobs:
   viewerjs:
     runs-on: ubuntu-latest
-    timeout-minutes: 25
+    timeout-minutes: 40
     steps:
       - uses: actions/checkout@v7
       - uses: actions/setup-python@v7