Update screenshot debug log output

The FORCE_UPDATE_ALL_GOLDENS is outdated now and replaced by
`--on-diff=update` from the new test runner.

Bug: none
Change-Id: I52f7f5f332753e7a8b3f989b67a9c2bdd8bee822
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/5934572
Auto-Submit: Jack Franklin <[email protected]>
Reviewed-by: Philip Pfaffe <[email protected]>
Commit-Queue: Philip Pfaffe <[email protected]>
Commit-Queue: Jack Franklin <[email protected]>

Author: jackfranklin

test/shared/screenshots.ts

@@ -305,7 +305,7 @@ async function compare(golden: string, generated: string, maximumDiffThreshold:
   if (isOnBot) {
     debugInfo = `${base64TestGeneratedImageLog}\n${base64DiffImageLog}\n`;
   } else {
-    debugInfo = `Run the tests again with FORCE_UPDATE_ALL_GOLDENS to update all tests that fail.
+    debugInfo = `Run the tests again with --on-diff=update to update all tests that fail.
   Only do this if you expected this screenshot to have changed!
 
   Diff image generated at: