Cleanup 'weirdinvert' remnants

Removed in 3baba1e7bc, but the docs
weren't updated.

runtime/doc/options.txt

@@ -7104,12 +7104,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 	has been changed.
 
 		     *'weirdinvert'* *'wiv'* *'noweirdinvert'* *'nowiv'*
-'weirdinvert' 'wiv'	boolean	(default off)
-			global
-	This option has the same effect as the 't_xs' terminal option.
-	It is provided for backwards compatibility with version 4.x.
-	Setting 'weirdinvert' has the effect of making 't_xs' non-empty, and
-	vice versa.  Has no effect when the GUI is running.
+'weirdinvert' 'wiv'	Removed. |vim-differences| {Nvim}
 
 						*'whichwrap'* *'ww'*
 'whichwrap' 'ww'	string	(Vim default: "b,s", Vi default: "")

runtime/doc/quickref.txt

@@ -918,7 +918,6 @@ Short explanation of each option:		*option-list*
 'virtualedit'	  've'	    when to use virtual editing
 'visualbell'	  'vb'	    use visual bell instead of beeping
 'warn'			    warn for shell command when buffer was changed
-'weirdinvert'	  'wiv'	    for terminals that have weird inversion method
 'whichwrap'	  'ww'	    allow specified keys to cross line boundaries
 'wildchar'	  'wc'	    command-line character for wildcard expansion
 'wildcharm'	  'wcm'     like 'wildchar' but also works when mapped

runtime/doc/vim_diff.txt

@@ -122,6 +122,7 @@ Other options:
   'textmode'
   'ttybuiltin'
   'ttymouse'
+  'weirdinvert'
 
 Other commands:
   :fixdel