Merge pull request ocaml#11793 from dra27/then-than

Typo in `String.cat` doc comment

(cherry picked from commit d0cdf4b)

Author: shindere

stdlib/string.mli

@@ -139,8 +139,8 @@ val concat : string -> string list -> string
 val cat : string -> string -> string
 (** [cat s1 s2] concatenates s1 and s2 ([s1 ^ s2]).
 
-    @raise Invalid_argument if the result is longer then
-    than {!Sys.max_string_length} bytes.
+    @raise Invalid_argument if the result is longer than
+    {!Sys.max_string_length} bytes.
 
     @since 4.13.0
 *)

stdlib/stringLabels.mli

@@ -139,8 +139,8 @@ val concat : sep:string -> string list -> string
 val cat : string -> string -> string
 (** [cat s1 s2] concatenates s1 and s2 ([s1 ^ s2]).
 
-    @raise Invalid_argument if the result is longer then
-    than {!Sys.max_string_length} bytes.
+    @raise Invalid_argument if the result is longer than
+    {!Sys.max_string_length} bytes.
 
     @since 4.13.0
 *)