Disable caching of icons asset for Chrome 84

Chrome 84 has a browser bug which leads to it not properly loading icons, if they are served from cache:

• gitlab-org/gitlab#230433 (closed)
• https://bugs.chromium.org/p/chromium/issues/detail?id=1107442

This issue is fixed in Chrome Canary and will be deployed in Chrome 85 in more than 4 weeks.

Proposal

In the meanwhile we could fix the issue for the Chrome 84 by doing the following:

If asset == https://gitlab.com/assets/icons-*.svg
    and User Agent == Chrome 84; then set
       Cache-Control: max-age=0

User Agents for Chrome 84:

Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.105 Safari/537.36
Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.105 Safari/537.36
Mozilla/5.0 (Windows NT 10.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.105 Safari/537.36

Example asset as of now:

• https://gitlab.com/assets/icons-36b4ec5e1b87dbfebdcb6b706f9d87ed6df58db01b82685550e88f0eb65ae5a6.svg