[rails6][Gemfile] Update sqlite3

For Rails 6.0, sqlite3 ~> 1.4 is required:

    LoadError:
      Error loading the 'sqlite3' Active Record adapter. Missing a gem
      it depends on? can't activate sqlite3 (~> 1.4), already activated
      sqlite3-1.3.13. Make sure all dependencies are added to Gemfile.

This was changed in rails here:

ManageIQ#20721 (comment)

And is only part of rails 6.0.0.0-rc1 and above.

Gemfile

@@ -76,7 +76,7 @@ gem "rubyzip",                        "~>2.0.0",       :require => false
 gem "rugged",                         "~>1.1",         :require => false
 gem "snmp",                           "~>1.2.0",       :require => false
 gem "sprockets",                      "~>3.7.2",       :require => false
-gem "sqlite3",                        "~>1.3.0",       :require => false
+gem "sqlite3",                        "~>1.4.0",       :require => false
 gem "sync",                           "~>0.5",         :require => false
 gem "sys-filesystem",                 "~>1.3.4"
 gem "terminal",                                        :require => false