fix(gerrit): return HTML titles in more cases

At present, we don't return HTML titles if there's a trailing slash,
or a patchset. Instead, just consume the / and anything after it.

This also fixes /123, because this is HTTP redirected to the full path
*with a trailing slash* which otherwise wouldn't get the title
injected.

Change-Id: Idfd0e67752880a37dce0b400a3c1cfc53fac2912
Reviewed-on: https://cl.tvl.fyi/c/depot/+/859
Reviewed-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI

third_party/gerrit/syntax_highlight_nix.patch

@@ -1,12 +0,0 @@
-diff --git a/polygerrit-ui/app/elements/diff/gr-syntax-layer/gr-syntax-layer.js b/polygerrit-ui/app/elements/diff/gr-syntax-layer/gr-syntax-layer.js
-index 1a0bbd9f50..0f2786a911 100644
---- a/polygerrit-ui/app/elements/diff/gr-syntax-layer/gr-syntax-layer.js
-+++ b/polygerrit-ui/app/elements/diff/gr-syntax-layer/gr-syntax-layer.js
-@@ -99,6 +99,7 @@ const LANGUAGE_MAP = {
-   'text/x-vhdl': 'vhdl',
-   'text/x-yaml': 'yaml',
-   'text/vbscript': 'vbscript',
-+  'application/x-mix-transfer': 'nix',
- };
- const ASYNC_DELAY = 10;
-