Merge branch 'docs/fix-mitmproxy-link' into 'master'

Fix link to mitmproxy installation

See merge request gitlab-org/gitlab-ce!21947

doc/user/project/container_registry.md

@@ -216,7 +216,7 @@ needs to trust the mitmproxy SSL certificates for this to work.
 
 The following installation instructions assume you are running Ubuntu:
 
-1. Install mitmproxy (see http://docs.mitmproxy.org/en/stable/install.html)
+1. [Install mitmproxy](https://docs.mitmproxy.org/stable/overview-installation/).
 1. Run `mitmproxy --port 9000` to generate its certificates.
    Enter <kbd>CTRL</kbd>-<kbd>C</kbd> to quit.
 1. Install the certificate from `~/.mitmproxy` to your system: