feat(3p/gerrit): Upgrade Gerrit and plugins to v3.4.0

Brings us back to a stable version of Gerrit instead of a random
commit. Note that Gerrit 3.4.1 is out, but due to a bug it can not be
built publicly because it accidentally points at a private
submodule (this is being fixed upstream).

Change-Id: I0376c63a649498cef999dfa99bfccba511f2c8da
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3444
Tested-by: BuildkiteCI
Reviewed-by: lukegb <lukegb@tvl.fyi>

third_party/gerrit/0003-Syntax-highlight-rules.pl.patch

@@ -1,4 +1,4 @@
-From 7c2e72527d177fd26505821e6297e6aa270a4f96 Mon Sep 17 00:00:00 2001
+From be348f64eda257ae0af1f89552548d3e8eca3688 Mon Sep 17 00:00:00 2001
 From: Luke Granger-Brown <git@lukegb.com>
 Date: Thu, 2 Jul 2020 23:02:43 +0100
 Subject: [PATCH 3/7] Syntax highlight rules.pl
@@ -8,7 +8,7 @@ Subject: [PATCH 3/7] Syntax highlight rules.pl
  1 file changed, 12 insertions(+), 1 deletion(-)
 
 diff --git a/polygerrit-ui/app/elements/diff/gr-syntax-layer/gr-syntax-layer.ts b/polygerrit-ui/app/elements/diff/gr-syntax-layer/gr-syntax-layer.ts
-index 2762ccc625..ebb5d9dad9 100644
+index 2762ccc625..598e14589f 100644
 --- a/polygerrit-ui/app/elements/diff/gr-syntax-layer/gr-syntax-layer.ts
 +++ b/polygerrit-ui/app/elements/diff/gr-syntax-layer/gr-syntax-layer.ts
 @@ -103,6 +103,10 @@ const LANGUAGE_MAP = new Map<string, string>([
@@ -35,12 +35,12 @@ index 2762ccc625..ebb5d9dad9 100644
      // The Gerrit API provides only content-type, but for other users of
      // gr-diff it may be more convenient to specify the language directly.
 -    return metaInfo.language ?? LANGUAGE_MAP.get(metaInfo.content_type);
-+    return metaInfo.language ?? 
++    return metaInfo.language ??
 +        FILENAME_OVERRIDES.get(this._basename(metaInfo.name)) ??
 +        LANGUAGE_MAP.get(metaInfo.content_type);
    }
  
    /**
 -- 
-2.29.2
+2.32.0