chore: bump chromium to 76.0.3809.77 (6-0-x) (#19357)

* chore: bump chromium in DEPS to 76.0.3809.75

* chore: bump chromium in DEPS to 76.0.3809.76

* chore: bump chromium in DEPS to 76.0.3809.77

DEPS

@@ -10,7 +10,7 @@ gclient_gn_args = [
 
 vars = {
   'chromium_version':
-    '76.0.3809.74',
+    '76.0.3809.77',
   'node_version':
     'v12.4.0',