fix: Update release branch for Docker build GHA (#2600)

Author: gs-olive

.github/workflows/docker_builder.yml

@@ -1,12 +1,12 @@
 name: 'Torch-TensorRT Docker Build'
 
-# Apply workflow only to main branch
+# Apply workflow only to main, nightly, release branches
 on:
   push:
     branches:
       - main
       - nightly
-      - release/2.1
+      - release/2.2
 
 # If pushes to main are made in rapid succession,
 # cancel existing docker builds and use newer commits