Increase timeout for docs-building job (#31002)

When a change by contributor touches a common provider code, it
triggers docs building for all providers, which on public
runners can take more than 45 minutes (the optimisations we had
in place limit most of the PRs with the list of providers to be
build in docs, but when the list is "all", it will take that long)

.github/workflows/ci.yml

@@ -662,7 +662,7 @@ jobs:
         if: always()
 
   docs:
-    timeout-minutes: 45
+    timeout-minutes: 90
     name: "Build docs"
     runs-on: "${{needs.build-info.outputs.runs-on}}"
     needs: [build-info, wait-for-ci-images]