Bump pkg-config from 1.3.7 to 1.3.8 (mastodon#11616)

Bumps [pkg-config](https://github.com/ruby-gnome2/pkg-config) from 1.3.7 to 1.3.8.
- [Release notes](https://github.com/ruby-gnome2/pkg-config/releases)
- [Changelog](https://github.com/ruby-gnome/pkg-config/blob/master/NEWS)
- [Commits](ruby-gnome/pkg-config@1.3.7...1.3.8)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

Gemfile.lock

@@ -423,7 +423,7 @@ GEM
     pg (1.1.4)
     pghero (2.3.0)
       activerecord (>= 5)
-    pkg-config (1.3.7)
+    pkg-config (1.3.8)
     premailer (1.11.1)
       addressable
       css_parser (>= 1.6.0)