doc: document GOEXPERIMENT=aliastypeparams in release notes

For #65614.

Change-Id: I05b20a80b1163e1d3927c2f763ef6b7d20e6a937
Reviewed-on: https://go-review.googlesource.com/c/go/+/590617


Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
TryBot-Bypass: Robert Griesemer <gri@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

doc/next/2-language.md

@@ -11,3 +11,7 @@ The "range" clause in a "for-range" loop now accepts iterator functions of the f
  as range expressions.
  Calls of the iterator argument function produce the iteration values for the "for-range" loop.
  For details see the [language spec](https://tip.golang.org/ref/spec#For_statements).
+
+<!-- go.dev/issue/46477, CL 566856, CL 586955, CL 586956 -->
+Go 1.23 includes preview support for [generic type aliases](/issue/46477).
+Building the toolchain with `GOEXPERIMENT=aliastypeparams` enables this feature.

doc/next/6-stdlib/99-minor/go/types/46477.md

-<!-- TODO: https://go.dev/issue/46477#issuecomment-2101270785 says:
-
+<!-- see ../../../../2-language.md -->
\ No newline at end of file
-> In the meantime, we believe it makes sense to go forward with the Alias API changes
-> proposed in #67143 for 1.23, even though type parameters won't be allowed during type
-> checking. This lets work commence on parameterized alias support in tools.
-
-relevant CLs:
-
-https://go.dev/cl/566856 ("go/types, types2: initial support for parameterized type aliases")
-https://go.dev/cl/586955 ("internal/goexperiment: add aliastypeparams GOEXPERIMENT flag")
-https://go.dev/cl/586956 ("go/types, types2: use GOEXPERIMENT to enable alias type parameters")
-
--->