Remove some 10.5 hacks

Library/Homebrew/download_strategy.rb

@@ -488,8 +488,6 @@ class SubversionDownloadStrategy < VCSDownloadStrategy
     # cache as it will make any changes to get the right revision.
     svncommand = target.directory? ? 'up' : 'checkout'
     args = ['svn', svncommand] + fetch_args
-    # SVN shipped with XCode 3.1.4 can't force a checkout.
-    args << '--force' unless MacOS.version == :leopard
     args << url unless target.directory?
     args << target
     args << '-r' << revision if revision

Library/Homebrew/utils.rb

@@ -187,8 +187,6 @@ def curl *args
   flags = flags.delete("#") if ARGV.verbose?
 
   args = [flags, HOMEBREW_USER_AGENT, *args]
-  # See https://github.com/Homebrew/homebrew/issues/6103
-  args << "--insecure" if MacOS.version < "10.6"
   args << "--verbose" if ENV['HOMEBREW_CURL_VERBOSE']
   args << "--silent" unless $stdout.tty?