minor: Improve 'concat' builtin documentation

Author: HugoGGuerrier

lkql_jit/language/src/main/java/com/adacore/lkql_jit/built_ins/BuiltInFunctions.java

@@ -271,7 +271,7 @@ protected String executeOnString(String fileName) {
 
     @BuiltInFunction(
         name = "concat",
-        doc = "Given a list of lists or strings, return a concatenated list or string"
+        doc = "Given a list, return the result of the concatenation of all its elements"
     )
     abstract static class ConcatExpr extends BuiltInBody {
 

user_manual/generated/std.rst

@@ -38,7 +38,7 @@ Builtin functions
 
 .. function:: concat(list)
 
-    Given a list of lists or strings, return a concatenated list or string
+    Given a list, return the result of the concatenation of all its elements
 
 .. function:: map(iterable, function)