Add 'tasks/agent.py' to global cache list

releasenotes/notes/modify-omnibus-cache-rules-7820b09b51256c0b.yaml

@@ -0,0 +1,12 @@
+# Each section from every release note are combined when the
+# CHANGELOG.rst is rendered. So the text needs to be worded so that
+# it does not depend on any information only available in another
+# section. This may mean repeating some details, but each section
+# must be readable independently of the other.
+#
+# Each section note must be formatted as reStructuredText.
+---
+fixes:
+  - |
+    Adds the tasks/agent.py file to the list of files used to
+    compute the global omnibus cache.

tasks/libs/common/omnibus.py

@@ -204,6 +204,7 @@ def omnibus_compute_cache_key(ctx, env: dict[str, str]) -> str:
             'omnibus/python-scripts',
             'omnibus/resources',
             'omnibus/omnibus.rb',
+            'tasks/agent.py',
             'deps',
             'bazel',
         ],