Remove HttpResponse.BodyHandlers.ofFile(Path) from banned method list in Java 21 signatures

[uschindler]

Followup of #214, this method must be removed in signatures files for Java 21.

[kwin]

Actually the fix is even backported to 17.0.7: https://bugs.openjdk.org/browse/JDK-8299353

[uschindler]

That's fine, but it is still not recommend to use that function. Because if you develop a library you do not know which exact version java runs on.