tests: remove temp tab homebrew_version override

This had to be added in #1750 to work around special-casing for tabs
generated with Homebrew versions < 1.1.6. Now that 1.1.6 is the current
version, we can remove this hack.

Library/Homebrew/test/tab_test.rb

@@ -33,10 +33,6 @@ class TabTests < Homebrew::TestCase
   def test_defaults
     tab = Tab.empty
 
-    # FIXME: remove this line after Homebrew 1.1.6 is released.
-    # See https://github.com/Homebrew/brew/pull/1750#discussion_r94254622
-    tab.homebrew_version = "1.1.6"
-
     assert_empty tab.unused_options
     assert_empty tab.used_options
     assert_nil tab.changed_files
@@ -199,10 +195,6 @@ class TabTests < Homebrew::TestCase
     stdlib = :libcxx
     tab = Tab.create(f, compiler, stdlib)
 
-    # FIXME: remove this line after Homebrew 1.1.6 is released.
-    # See https://github.com/Homebrew/brew/pull/1750#discussion_r94254622
-    tab.homebrew_version = "1.1.6"
-
     runtime_dependencies = [
       { "full_name" => "bar", "version" => "2.0" },
       { "full_name" => "user/repo/from_tap", "version" => "1.0" },