Bump pg from 1.5.3 to 1.5.7 (#769)

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -242,7 +242,7 @@ GEM
     parser (3.3.3.0)
       ast (~> 2.4.1)
       racc
-    pg (1.5.3)
+    pg (1.5.7)
     psych (5.1.2)
       stringio
     public_suffix (5.0.5)