ci: update paths in a publish module api doc workflow

Module API documentation is described in Doxygen comments in C/C++ files
in src/ directory. No sense to run this job for other changes. The patch
changes paths in workflow accordingly.

NO_CHANGELOG=ci
NO_DOC=ci
NO_TEST=ci

(cherry picked from commit 9af36ae1)

.github/workflows/publish-module-api-doc.yaml

@@ -4,6 +4,9 @@ on:
   push:
     branches:
       - 'master'
+    paths:
+      - '.github/workflows/publish-module-api-doc.yaml'
+      - 'src/**'
   pull_request:
   workflow_dispatch: