Fix pipeline completion trigger description

**Why?**

Resolves: awslabs#654.

The description of the pipeline completion triggers did not parse the dynamic
parameters that were defined.

src/lambda_codebase/initial_commit/bootstrap_repository/adf-build/shared/cdk/cdk_constructs/adf_events.py

@@ -119,7 +119,7 @@ def __init__(self, scope: Construct, id: str, params: dict, **kwargs):
                 _event = _events.Rule(
                     self,
                     f'completion_{pipeline}',
-                    description="Triggers {pipeline} on completion of {params['pipeline']}",
+                    description=f"Triggers {pipeline} on completion of {params['pipeline']}",
                     enabled=True,
                     event_pattern=_events.EventPattern(
                         detail={