ci: give the Linux coverage lane the hosted image's teardown budget

The managed-scope disposal cases in subprocess-local and bash-sandbox run past
the 5000ms default when this lane's four partitions, six workers per gate, and
sibling gates share one host. The same commit stays inside the budget on the
in-house pool: the hosted image exceeded it (run 34449848541) and the lane is
green with 90000 (run 34457655892). The Windows coverage lane already grants
the same budget for the same class of teardown.

(cherry picked from commit bf3468adf0947a51f09d4a1aaae2865f3e50a2f2)

.github/workflows/ci.yml

@@ -121,6 +121,14 @@ jobs:
       DSH_COVERAGE_MAX_WORKERS: '6'
       DSH_COVERAGE_PARTITIONS: '4'
       DSH_GATE_CONCURRENCY: '3'
+      # Managed-scope teardown cases run past the default per-test budget when
+      # this lane's partitions, workers, and sibling gates share one host: the
+      # disposal cases in subprocess-local and bash-sandbox exceeded 5000ms on
+      # the hosted image (run 34449848541) while the same commit stayed inside
+      # the budget on the in-house pool; the lane is green with this value
+      # (run 34457655892). The Windows coverage lane grants the same budget for
+      # the same reason.
+      DSH_COVERAGE_TEST_TIMEOUT_MS: '90000'
       # A gate failure aborts the sibling gate instead of waiting out its
       # multi-minute instrumented run.
       DSH_GATE_FAIL_FAST: '1'