Do not lock airbrake in Gemfile

There is not reason to not use new versions of airbrake. Update to last
version 9.0.0.

Gemfile

@@ -142,7 +142,7 @@ gem 'axlsx', git: 'https://github.com/randym/axlsx.git'
 gem 'axlsx_rails'
 
 # as error catcher
-gem 'airbrake', '~> 7.1'
+gem 'airbrake'
 
 # to make links faster
 gem 'turbolinks'

Gemfile.lock

@@ -64,9 +64,10 @@ GEM
     addressable (2.6.0)
       public_suffix (>= 2.0.2, < 4.0)
     afm (0.2.2)
-    airbrake (7.4.0)
-      airbrake-ruby (~> 2.12)
-    airbrake-ruby (2.12.0)
+    airbrake (9.0.0)
+      airbrake-ruby (~> 4.2)
+    airbrake-ruby (4.2.2)
+      rbtree3 (~> 0.5)
     ajax-datatables-rails (0.4.3)
       railties (>= 4.0)
     archive-zip (0.12.0)
@@ -436,6 +437,7 @@ GEM
     rb-fsevent (0.10.3)
     rb-inotify (0.10.0)
       ffi (~> 1.0)
+    rbtree3 (0.5.0)
     rdoc (6.0.4)
     rdoc-generator-fivefish (0.4.0)
       inversion (~> 1.1)
@@ -607,7 +609,7 @@ DEPENDENCIES
   active_model_serializers
   acts_as_commentable_with_threading
   acts_as_list
-  airbrake (~> 7.1)
+  airbrake
   ajax-datatables-rails
   autoprefixer-rails
   awesome_nested_set