Bump guard-bundler from 3.0.1 to 3.1.0 (#327)

Author: dependabot[bot]

Gemfile.lock

@@ -62,8 +62,8 @@ GEM
       pry (>= 0.13.0)
       shellany (~> 0.0)
       thor (>= 0.18.1)
-    guard-bundler (3.0.1)
-      bundler (>= 2.1, < 3)
+    guard-bundler (3.1.0)
+      bundler (>= 2.1, < 5)
       guard (~> 2.2)
       guard-compat (~> 1.1)
     guard-compat (1.2.1)