Add filter to trigger only on events from dependabot branches

Author: Oleg

.github/workflows/dependabot-build.yml

@@ -4,6 +4,8 @@ on:
   workflow_run: # zizmor: ignore[dangerous-triggers] we are aware that it is a dengerouse trigger but we need a way to build an image after Dependabot PR
     types: [ completed ]
     workflows: [ 'Rebuild Bowtie Image' ]
+    branches:
+      - 'dependabot/**'
 
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