fix(colored-man-pages): add env GROFF_NO_SGR=1 (#11831)

plugins/colored-man-pages/colored-man-pages.plugin.zsh

@@ -36,6 +36,7 @@ function colored() {
   # Prefer `less` whenever available, since we specifically configured
   # environment for it.
   environment+=( PAGER="${commands[less]:-$PAGER}" )
+  environment+=( GROFF_NO_SGR=1 )
 
   # See ./nroff script.
   if [[ "$OSTYPE" = solaris* ]]; then