restored main in CI cpp check

.github/workflows/cpp-check.yaml

@@ -25,7 +25,7 @@ on:
       zenoh_cpp_branch:
         description: 'Branch of zenoh-cpp to use'
         required: false
-        default: 'liveliness_stabilize'
+        default: 'main'
 
 jobs:
   build-and-test:
@@ -52,7 +52,7 @@ jobs:
         git clone https://github.com/eclipse-zenoh/zenoh-cpp.git
         cd zenoh-cpp
         git fetch --all
-        git checkout ${{ github.event.inputs.zenoh_cpp_branch || 'liveliness_stabilize' }}
+        git checkout ${{ github.event.inputs.zenoh_cpp_branch || 'main' }}
         git submodule update --init --recursive
 
     - name: build zenoh-cpp