Modify pc/ WATCHLISTS definition

Bug: None
Change-Id: I187981ac0dd16c7da299208e8dc351a686e8eea9
No-Try: True
Reviewed-on: https://webrtc-review.googlesource.com/c/120820
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Reviewed-by: Seth Hampson <shampson@webrtc.org>
Commit-Queue: Seth Hampson <shampson@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26500}
diff --git a/WATCHLISTS b/WATCHLISTS
index 4260bf9..c56a69d 100644
--- a/WATCHLISTS
+++ b/WATCHLISTS
@@ -95,7 +95,7 @@
       'filepath': 'system_wrappers/.*',
     },
     'pc': {
-      'filepath': 'pc/.*',
+      'filepath': '^pc/.*',
     },
   },