DEV: Don't warn on missing git tags (#15507)

Fixes the following output in specs: ``` fatal: No names found, cannot describe anything. ```
2022-01-09 20:25:58 +01:00 · 2022-01-09 20:25:58 +01:00 · 40147ca2ee
parent 5c74f048a5
commit 40147ca2ee
1 changed files with 1 additions and 1 deletions
--- a/lib/discourse.rb
+++ b/lib/discourse.rb
@ -667,7 +667,7 @@ module Discourse

  def self.full_version
    @full_version ||= begin
-      git_cmd = 'git describe --dirty --match "v[0-9]*"'
+      git_cmd = 'git describe --dirty --match "v[0-9]*" 2> /dev/null'
      self.try_git(git_cmd, 'unknown')
    end
  end