Revert "Use osc's devel_project implementation instead"

There is only one case where this is invoked, and there we want
to check not whether osc's git lookup finds a devel project but
we want to check whether the "legacy" meta pkg still has a devel project
set.

This reverts commit e46b29016f.

lib/obs.py

@@ -124,8 +124,11 @@ class OBS:
         return root.get("project") == project
 
     def devel_project(self, project, package):
-        develprj, _ = osc.core.show_devel_project(self.url, project, package)
-        return develprj
+        root = self._meta(f"{project}/{package}")
+        devel = root.find("devel")
+        if devel is None:
+            return None
+        return devel.get("project")
 
     def request(self, requestid):
         root = self._request(requestid)