text/regex: Remove old docmentation and unneeded flag

`Unsupported_Flag` was used back when the iterator did not handle
`.Multiline`.

core/text/regex/regex.odin

@@ -28,8 +28,6 @@ Creation_Error :: enum {
 	Expected_Delimiter,
 	// An unknown letter was supplied to `create_by_user` after the last delimiter.
 	Unknown_Flag,
-	// An unsupported flag was supplied.
-	Unsupported_Flag,
 }
 
 Error :: union #shared_nil {
@@ -69,7 +67,6 @@ Regular_Expression :: struct {
 
 /*
 An iterator to repeatedly match a pattern against a string, to be used with `*_iterator` procedures.
-Note: Does not handle `.Multiline` properly.
 */
 Match_Iterator :: struct {
 	regex:    Regular_Expression,
@@ -436,7 +433,6 @@ match_with_preallocated_capture :: proc(
 
 /*
 Iterate over a `Match_Iterator` and return successive captures.
-Note: Does not handle `.Multiline` properly.
 
 Inputs:
 - it: Pointer to the `Match_Iterator` to iterate over.