docs(man(R)): fix a typo

Signed-off-by: Masatake YAMATO <[email protected]>

Author: masatake

docs/man/ctags-lang-r.7.rst

@@ -14,7 +14,7 @@ SYNOPSIS
 --------
 |	**ctags** ... --languages=+R ...
 |	**ctags** ... --language-force=R ...
-|	**ctags** ... --map-Python=+.r ...
+|	**ctags** ... --map-R=+.r ...
 
 DESCRIPTION
 -----------

man/ctags-lang-r.7.rst.in

@@ -14,7 +14,7 @@ SYNOPSIS
 --------
 |	**@CTAGS_NAME_EXECUTABLE@** ... --languages=+R ...
 |	**@CTAGS_NAME_EXECUTABLE@** ... --language-force=R ...
-|	**@CTAGS_NAME_EXECUTABLE@** ... --map-Python=+.r ...
+|	**@CTAGS_NAME_EXECUTABLE@** ... --map-R=+.r ...
 
 DESCRIPTION
 -----------