manual: replace an obsolete collation example with a valid one

In the Spanish language, the digraph "ll" has not been considered a
separate letter since 1994:
  https://www.rae.es/consultas/exclusion-de-ch-y-ll-del-abecedario

Since January 1998 (commit 49891c106244888123557fca7fddda4fa1f96b1d),
glibc's locale data no longer specifies "ch" and "ll" as separate
collation elements.  So, it's better to not use "ll" in an example.

Also, the Czech "ch" is a better example as it collates in a more
surprising place.

1 files changed, 3 insertions, 3 deletions

diff --git a/manual/string.texi b/manual/string.texi
index 23f516439a..ad11519377 100644
--- a/manual/string.texi
+++ b/manual/string.texi
@@ -1422,9 +1422,9 @@ This is an obsolete alias for @code{memcmp}, derived from BSD.
 In some locales, the conventions for lexicographic ordering differ from
 the strict numeric ordering of character codes.  For example, in Spanish
 most glyphs with diacritical marks such as accents are not considered
-distinct letters for the purposes of collation.  On the other hand, the
-two-character sequence @samp{ll} is treated as a single letter that is
-collated immediately after @samp{l}.
+distinct letters for the purposes of collation.  On the other hand, in
+Czech the two-character sequence @samp{ch} is treated as a single letter
+that is collated between @samp{h} and @samp{i}.
 
 You can use the functions @code{strcoll} and @code{strxfrm} (declared in
 the headers file @file{string.h}) and @code{wcscoll} and @code{wcsxfrm}