Upgrade charlock_holmes to v0.7.7

This fixes some build issues on MacOS:
https://github.com/brianmario/charlock_holmes/compare/0.7.6..v0.7.7

Gemfile

@@ -264,7 +264,7 @@ gem 'licensee', '~> 8.9'
 gem 'ace-rails-ap', '~> 4.1.0'
 
 # Detect and convert string character encoding
-gem 'charlock_holmes', '~> 0.7.5'
+gem 'charlock_holmes', '~> 0.7.7'
 
 # Detect mime content type from content
 gem 'mimemagic', '~> 0.3.2'

Gemfile.lock

@@ -142,7 +142,7 @@ GEM
       mime-types (>= 1.16)
     cause (0.1)
     character_set (1.1.2)
-    charlock_holmes (0.7.6)
+    charlock_holmes (0.7.7)
     childprocess (0.9.0)
       ffi (~> 1.0, >= 1.0.11)
     chronic (0.10.2)
@@ -1143,7 +1143,7 @@ DEPENDENCIES
   capybara (~> 3.22.0)
   capybara-screenshot (~> 1.0.22)
   carrierwave (~> 1.3)
-  charlock_holmes (~> 0.7.5)
+  charlock_holmes (~> 0.7.7)
   chronic (~> 0.10.2)
   commonmarker (~> 0.20)
   concurrent-ruby (~> 1.1)