gr-repo-commands: Use h2 for "Run GC"

Release-Notes: gr-repo-commands: Use h2 for "Run GC"
Change-Id: Ifedc5e858955cc64f43c9556a1dc0d3aacd6e34c
(cherry picked from commit 93a64d4cfce8295be1f8eff864c13baef9fa6417)

polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts

diff --git a/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts b/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts
index 1a0eeea..7edfe2b 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts
+++ b/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts
@@ -208,7 +208,7 @@
       return;
 
     return html`
-      <h3 class="heading-3">${this.repoConfig?.actions['gc']?.label}</h3>
+      <h2 class="heading-2">${this.repoConfig?.actions['gc']?.label}</h2>
       <gr-button
         title=${this.repoConfig?.actions['gc']?.title || ''}
         ?loading=${this.runningGC}