wikiheaders: Don't escape `.` chars in manpage's brief section.

Otherwise, the `apropos` command gets upset.

Fixes #15387.

(cherry picked from commit a49a5e87a9fa41a12da32fca98987beef84964fc)

build-scripts/wikiheaders.pl

@@ -2912,6 +2912,11 @@ __EOF__
         $brief = shift @briefsplit;
         $brief = dewikify($wikitype, $brief);
 
+        # Hack: `apropros` doesn't like escaped character things like `\[char46]` for `.`...since almost every
+        # manpage will end their Brief section with a period and it won't wordwrap to risk being a groff control
+        # character, just replace it.
+        $brief =~ s/\\\[char46\]/./g;
+
         if (defined $remarks) {
             $remarks = dewikify($wikitype, join("\n", @briefsplit) . $remarks);
         }