Bump pkg-config from 1.3.8 to 1.3.9 (#12011)

Bumps [pkg-config](https://github.com/ruby-gnome/pkg-config) from 1.3.8 to 1.3.9.
- [Release notes](https://github.com/ruby-gnome/pkg-config/releases)
- [Changelog](https://github.com/ruby-gnome/pkg-config/blob/master/NEWS)
- [Commits](https://github.com/ruby-gnome/pkg-config/compare/1.3.8...1.3.9)

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

Gemfile.lock

@@ -435,7 +435,7 @@ GEM
     pg (1.1.4)
     pghero (2.3.0)
       activerecord (>= 5)
-    pkg-config (1.3.8)
+    pkg-config (1.3.9)
     premailer (1.11.1)
       addressable
       css_parser (>= 1.6.0)