[DevTools] Use insecure styling for optionally blockable mixed content
[DevTools] Use insecure styling for optionally blockable mixed content

Currently, optionally blockable mixed content has the neutral styling in
the sidebar. This cl brings the styling to match that of blockable mixed
content and deletes now unneeded code.

Screenshot: https://drive.google.com/file/d/1jndlsqyPHYlPNYDBM0Azdi94ezEvUYQm/view?usp=sharing

Bug: 941055
Change-Id: Ia9ace8cd0345ee5df877d61662723d515d5c4629
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1531520
Reviewed-by: Erik Luo <26192f5e05d23e5ee959014fb911d780e566545b@chromium.org>
Commit-Queue: Livvie Lin <54c2345d0b1f4eb63337755673bca72b0ada932d@chromium.org>
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#642810}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: c88b9ec1d93a15cd204c556b62b0a6dce9af0f91
ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend