Update Chrome & Firefox version in DEPS to 131.0.6778.3 & 131.0.3 respectively

Change-Id: Ia3e8a90152099ec73f0c115cf8f8bb043a1649ca
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/391180
Auto-Submit: Nate Biggs <[email protected]>
Reviewed-by: Sigmund Cherem <[email protected]>
Commit-Queue: Nate Biggs <[email protected]>
Commit-Queue: Sigmund Cherem <[email protected]>

Author: natebiggs

DEPS

@@ -206,9 +206,9 @@ vars = {
   # meant to be downloaded by users for local testing. You can self-service
   # update these by following the go/dart-engprod/browsers.md instructions.
   "download_chrome": False,
-  "chrome_tag": "130.0.6723.31",
+  "chrome_tag": "131.0.6778.3",
   "download_firefox": False,
-  "firefox_tag": "131.0",
+  "firefox_tag": "131.0.3",
 
   # Emscripten is used in dart2wasm tests.
   "download_emscripten": False,