Bump guard from 2.15.0 to 2.15.1 (#3909) [ci skip]

Bumps [guard](https://github.com/guard/guard) from 2.15.0 to 2.15.1.
- [Release notes](https://github.com/guard/guard/releases)
- [Commits](https://github.com/guard/guard/compare/v2.15.0...v2.15.1)

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

Gemfile.lock

@@ -379,7 +379,7 @@ GEM
       multi_json (~> 1.11)
       os (>= 0.9, < 2.0)
       signet (~> 0.7)
-    guard (2.15.0)
+    guard (2.15.1)
       formatador (>= 0.2.4)
       listen (>= 2.7, < 4.0)
       lumberjack (>= 1.0.12, < 2.0)
@@ -499,7 +499,7 @@ GEM
     nio4r (2.4.0)
     nokogiri (1.10.4)
       mini_portile2 (~> 2.4.0)
-    notiffany (0.1.1)
+    notiffany (0.1.3)
       nenv (~> 0.1)
       shellany (~> 0.0)
     oauth (0.5.4)