Update the `browser` gem.

- Need the `mobile?` detection (that the new version provides) for the
  U2F registration/ authentication flow

Gemfile

@@ -48,7 +48,7 @@ gem 'attr_encrypted', '~> 3.0.0'
 gem 'u2f', '~> 0.2.1'
 # Browser detection
-gem "browser", '~> 1.0.0'
+gem "browser", '~> 2.0.3'
 # Extracting information from a git repository
 # Provide access to Gitlab::Git library

Gemfile.lock

@@ -92,7 +92,7 @@ GEM
       sass (~> 3.0)
       slim (>= 1.3.6, < 4.0)
       terminal-table (~> 1.4)
-    browser (1.0.1)
+    browser (2.0.3)
     builder (3.2.2)
     bullet (5.0.0)
       activesupport (>= 3.0.0)
@@ -815,7 +815,7 @@ DEPENDENCIES
   binding_of_caller (~> 0.7.2)
   bootstrap-sass (~> 3.3.0)
   brakeman (~> 3.2.0)
-  browser (~> 1.0.0)
+  browser (~> 2.0.3)
   bullet
   bundler-audit
   byebug
@@ -977,4 +977,4 @@ DEPENDENCIES
   wikicloth (= 0.8.1)
 BUNDLED WITH
-   1.12.4
+   1.12.5

app/views/help/_shortcuts.html.haml

@@ -24,7 +24,7 @@
                 %td Show/hide this dialog
               %tr
                 %td.shortcut
-                  - if browser.mac?
+                  - if browser.platform.mac?
                     .key ⌘ shift p
                   - else
                     .key ctrl shift p