Include https:// in README.chromium URL

As witnessed in the referenced bug, automation expects the scheme to be
present, and files a bug otherwise.

Bug: chromium:428783320
Change-Id: Ie156cafe5dac7ca8d0a2602ab3f13e08dc5fe7fb
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6694572
Auto-Submit: Mathias Bynens <[email protected]>
Commit-Queue: Alex Rudenko <[email protected]>
Commit-Queue: Mathias Bynens <[email protected]>
Reviewed-by: Alex Rudenko <[email protected]>

Author: mathiasbynens

front_end/third_party/chromium/README.chromium

@@ -1,7 +1,8 @@
 Name: Dependencies sourced from the upstream `chromium` repository
 URL: https://source.chromium.org/chromium/chromium/src/+/main:components/variations/proto/devtools/
+Version: N/A
 Revision: 8364c85ec0d463ecc98675f747e6a09134d2e07c
-Update Mechanism: Manual (crbug.com/428069060)
+Update Mechanism: Manual (https://crbug.com/428069060)
 License: BSD-3-Clause
 License File: LICENSE
 Shipped: yes