fix(codepipeline-actions): correctly name the triggering Event in Cod…

…eCommitSourceAction (#10706)

Use backticks instead of single quotes for template strings.

Fixes #10665

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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-codepipeline-actions/lib/codecommit/source-action.ts

@@ -165,7 +165,7 @@ export class CodeCommitSourceAction extends Action {
       } while (this.props.repository.node.tryFindChild(candidate) !== undefined);
       return candidate;
     } else {
-      const branchIdDisambiguator = this.branch === 'master' ? '' : '-${this.branch}-';
+      const branchIdDisambiguator = this.branch === 'master' ? '' : `-${this.branch}-`;
       return this.eventIdFromPrefix(`${baseId}${branchIdDisambiguator}`);
     }
   }