Use src not src/sage

Author: kwankyu

src/bin/sage-runtests

@@ -172,9 +172,9 @@ if __name__ == "__main__":
         if args.verbose:
             pytest_options.append("-v")
 
-        # #35999: no filenames in arguments is equivalent to "src/sage"
+        # #35999: no filenames in arguments is equivalent to "src"
         if not args.filenames:
-            filenames = [os.path.join(os.environ.get('SAGE_SRC'), "sage")]
+            filenames = [os.environ.get('SAGE_SRC')]
         else:
             # #31924: Do not run pytest on individual Python files unless
             # they match the pytest file pattern.  However, pass names