[Dark mode] make changesSidebar.css consistent with sources sidebar
[Dark mode] make changesSidebar.css consistent with sources sidebar

Bug: chromium:1152736, chromium:1210894
Change-Id: I6b3b9af30fbe0b0e1fdddb6c10a4bc4647909093
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2910103
Commit-Queue: Jack Franklin <993fcadce4d04090da2fefd557a0995e7966c8d5@chromium.org>
Commit-Queue: Paul Lewis <8915f5d5c39a08c5a3e8a8d7314756e4580816f9@chromium.org>
Auto-Submit: Jack Franklin <993fcadce4d04090da2fefd557a0995e7966c8d5@chromium.org>
Reviewed-by: Paul Lewis <8915f5d5c39a08c5a3e8a8d7314756e4580816f9@chromium.org>

ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend