Fix an error message

Bug: none
Change-Id: Ia62aac731e4c33e7a424eda451edb81151faba52
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6054334
Auto-Submit: Philip Pfaffe <[email protected]>
Commit-Queue: Alex Rudenko <[email protected]>
Commit-Queue: Philip Pfaffe <[email protected]>
Reviewed-by: Alex Rudenko <[email protected]>

Author: pfaffe

test/shared/snapshots.ts

@@ -62,7 +62,7 @@ const saveSnapshotsIfTaken = () => {
 const restoreSnapshots = () => {
   if (!currentSnapshotPath || !existsSync(currentSnapshotPath)) {
     throw new Error(`Could not find snapshot for ${
-        currentSnapshotPath}. You can update the snapshots by running the tests with --diff=update.`);
+        currentSnapshotPath}. You can update the snapshots by running the tests with --on-diff=update.`);
   }
   currentSnapshot = JSON.parse(readFileSync(currentSnapshotPath, 'utf-8'));
 };