Fix links to source examples in Airflow docs (apache#50082)

While apache#49978 added back source links and it nicely works for
the providers, there was still a problem with links to sources in
Airflow - they were prefixed with extra `src`. This PR fixes it.

Author: potiuk

devel-common/src/sphinx_exts/exampleinclude.py

@@ -195,6 +195,9 @@ def create_node(env, relative_path, show_button):
     if relative_path.startswith("airflow-core/src/"):
         relative_path = relative_path.replace("airflow-core/src/", "", 1)
 
+    if relative_path.startswith("src/"):
+        relative_path = relative_path.replace("src/", "", 1)
+
     if relative_path.endswith(".py"):
         pagename = "_modules/" + relative_path[:-3]
     else: