fix variable typon in libs release (canonical#124)

.github/workflows/charm-release.yaml

@@ -65,7 +65,7 @@ jobs:
           # Get the libs folder name
           libraries_folder=$(yq .name metadata.yaml | tr - _)
           # For each library belonging to the charm, publish it
-          for lib in $(find lib/charms/$libs_folder -type f | sed 's|lib/||' | sed 's/.py//' | sed 's|/|.|g'); do
+          for lib in $(find lib/charms/$libraries_folder -type f | sed 's|lib/||' | sed 's/.py//' | sed 's|/|.|g'); do
             charmcraft publish-lib $lib
           done
         env: