(Docs) Remove spec change documents for records & pattern matching

Two language/VM features were made final in Java 16, and their specification changes were applied to JLS & JVMS. Their spec change documents should no longer be present in JDK 17.

- Records (JEP 395), including records-jls, records-jvms, records-serialization, class-terminology-jls, and local-statics-jls
- Pattern Matching for instanceof (JEP 394), including patterns-instanceof-jls