Bump font-awesome-sass from 4.7.0 to 5.15.1

Bumps [font-awesome-sass](https://github.com/FortAwesome/font-awesome-sass) from 4.7.0 to 5.15.1.
- [Release notes](https://github.com/FortAwesome/font-awesome-sass/releases)
- [Commits](FortAwesome/font-awesome-sass@4.7.0...5.15.1)

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

Author: dependabot-preview[bot]

Gemfile.lock

@@ -92,9 +92,9 @@ GEM
       request_store (>= 1.0)
     erubi (1.10.0)
     execjs (2.7.0)
-    ffi (1.11.3)
-    font-awesome-sass (4.7.0)
-      sass (>= 3.2)
+    ffi (1.14.2)
+    font-awesome-sass (5.15.1)
+      sassc (>= 1.11)
     globalid (0.4.2)
       activesupport (>= 4.2.0)
     i18n (1.8.5)
@@ -158,9 +158,6 @@ GEM
       rake (>= 0.8.7)
       thor (~> 1.0)
     rake (13.0.3)
-    rb-fsevent (0.10.3)
-    rb-inotify (0.10.1)
-      ffi (~> 1.0)
     rdoc (6.2.1)
     redis (4.2.2)
     ref (2.0.0)
@@ -170,11 +167,6 @@ GEM
     ruby-nmap (0.10.0)
       nokogiri (~> 1.3)
       rprogram (~> 0.3)
-    sass (3.7.4)
-      sass-listen (~> 4.0.0)
-    sass-listen (4.0.0)
-      rb-fsevent (~> 0.9, >= 0.9.4)
-      rb-inotify (~> 0.9, >= 0.9.7)
     sass-rails (6.0.0)
       sassc-rails (~> 2.1, >= 2.1.1)
     sassc (2.2.0)