Fix BK DRA pipeline (#39212)

This commit fixes the error
"interpolating remaining fields: Expected identifier to start with a letter, got /"

.buildkite/packaging.pipeline.yml

@@ -16,7 +16,7 @@ steps:
     key: dashboards
     steps:
       - label: Snapshot dashboards
-        if: build.branch =~ /^\d+\.\d+$/ || build.branch == 'main' || build.env('RUN_SNAPSHOT') == "true"
+        if: build.branch =~ /^\d+\.\d+$$/ || build.branch == 'main' || build.env('RUN_SNAPSHOT') == "true"
         key: dashboards-snapshot
         # TODO: container with go and make
         agents:
@@ -32,7 +32,7 @@ steps:
           - build/distributions/**/*
 
       - label: Staging dashboards
-        if: build.branch =~ /^\d+\.\d+$/
+        if: build.branch =~ /^\d+\.\d+$$/
         key: dashboards-staging
         # TODO: container with go and make
         agents:
@@ -46,7 +46,7 @@ steps:
           - build/distributions/**/*
 
   - group: Packaging snapshot
-    if: build.branch =~ /^\d+\.\d+$/ || build.branch == 'main' || build.env('RUN_SNAPSHOT') == "true"
+    if: build.branch =~ /^\d+\.\d+$$/ || build.branch == 'main' || build.env('RUN_SNAPSHOT') == "true"
     key: packaging-snapshot
     steps:
       - label: "SNAPSHOT: {{matrix}}"
@@ -119,7 +119,7 @@ steps:
 
     key: packaging-staging
     ## Only for release
-    if: build.branch =~ /^\d+\.\d+$/
+    if: build.branch =~ /^\d+\.\d+$$/
     steps:
       - label: "STAGING: {{matrix}}"
         env:
@@ -192,7 +192,7 @@ steps:
     steps:
       - label: DRA Snapshot
         ## Only for release branches and main
-        if: build.branch =~ /^\d+\.\d+$/ || build.branch == 'main' || build.env('RUN_SNAPSHOT') == "true"
+        if: build.branch =~ /^\d+\.\d+$$/ || build.branch == 'main' || build.env('RUN_SNAPSHOT') == "true"
         key: dra-snapshot
         env:
           DRA_WORKFLOW: snapshot
@@ -210,7 +210,7 @@ steps:
 
       - label: DRA Staging
         ## Only for release branches
-        if: build.branch =~ /^\d+\.\d+$/
+        if: build.branch =~ /^\d+\.\d+$$/
         key: dra-staging
         env:
           DRA_WORKFLOW: staging