man.vim: Document how to disable bold highlighting

Closes #11435

runtime/doc/filetype.txt

@@ -549,7 +549,9 @@ Variables:
 *b:man_default_sects*       Comma-separated, ordered list of preferred sections.
                           For example in C one usually wants section 3 or 2: >
                                :let b:man_default_sections = '3,2'
-*g:man_hardwrap*            Hard-wrap to $MANWIDTH. May improve layout.
+*g:man_hardwrap*            Hard-wrap to $MANWIDTH or window width if $MANWIDTH is
+                          empty. Enabled by default. Disable to enable soft
+                          wrapping.
 
 To use Nvim as a manpager: >
      export MANPAGER='nvim +Man!'
@@ -563,6 +565,9 @@ soft wrapped as with `:Man`. You can set in your environment: >
 
 So `groff`'s pre-formatting output will be the same as with `:Man` i.e soft-wrapped.
 
+To disable bold highlighting: >
+     :highlight link manBold Normal
+
 PDF							*ft-pdf-plugin*
 
 Two maps, <C-]> and <C-T>, are provided to simulate a tag stack for navigating