Add jetty-12.0 relevant content to README.md (#10858)

Co-authored-by: Lauri Tulmin <tulmin@gmail.com>

instrumentation/jetty/README.md

@@ -5,8 +5,5 @@ Jetty support is divided into the following sub-modules:
 - `jetty-common:javaagent` contains common type instrumentation and advice helper classes used by
   the `javaagent` modules of all supported Jetty versions
 - `jetty-8.0:javaagent` applies Jetty request handler instrumentation for versions `[8, 11)`
-- `jetty-11.0:javaagent` applies Jetty request handler instrumentation for versions `[11,)`
-
-Instrumentations in `jetty-8.0` and `jetty-11.0` are mutually exclusive, this is guaranteed by the
-instrumentation requiring parameters with types from packages `javax.servlet` or `jakarta.servlet`
-respectively.
+- `jetty-11.0:javaagent` applies Jetty request handler instrumentation for versions `[11,12)`
+- `jetty-12.0:javaagent` applies Jetty request handler instrumentation for versions `[12,)`