ci(test-unit): raise job timeout to 60m for the three 55m shards

caching-local, proxy-extras and enterprise-package gave pytest 20m but
capped the job at 55m; with a 35m setup ceiling plus 5m of runner
overhead the job deadline could preempt pytest itself.

.github/workflows/test-unit.yml

@@ -211,7 +211,7 @@ jobs:
             workers: 2
             reruns: 2
             timeout-minutes: 20
-            job-timeout-minutes: 55
+            job-timeout-minutes: 60
 
           - shard: proxy-extras
             artifact-name: proxy-extras
@@ -219,7 +219,7 @@ jobs:
             workers: 2
             reruns: 2
             timeout-minutes: 20
-            job-timeout-minutes: 55
+            job-timeout-minutes: 60
 
           - shard: enterprise-package
             artifact-name: enterprise-package
@@ -227,7 +227,7 @@ jobs:
             workers: 4
             reruns: 2
             timeout-minutes: 20
-            job-timeout-minutes: 55
+            job-timeout-minutes: 60
 
           - shard: responses-caching-types
             artifact-name: responses-caching-types