find.1: access ~ character portably

* find/find.1:
The `\(ti` special character escape sequence is not universally
portable.  Indirect it through a string definition.  (GNU Bash also uses
this technique.[1])

[1] a8a1c2fac0/doc/bash.1 (L26)

Discussed at:
https://lists.gnu.org/r/bug-findutils/2025-11/msg00094.html

Copyright-paperwork-exempt: Yes

find/find.1

@@ -3,12 +3,14 @@
 .ie \n(.g \{\
 .  ds "  \(dq
 .  ds '  \(aq
+.  ds ~  \(ti
 .  ds en \(en
 .\}
 .el \{\
 .  \" \*" is not usable in macro arguments on AT&T troff.
 .  ds "  ""\" two adjacent quotes and no space before this comment
 .  ds '  '
+.  ds ~  ~
 .  ds en \-
 .\}
 .SH NAME
@@ -2513,7 +2515,7 @@ to
 but omit files and directories named
 .I .snapshot
 (and anything in them).  It also omits files or directories whose name ends in
-`\(ti', but not their contents.
+`\*~', but not their contents.
 .nf
 \&
 .in +4n