RFR: JDK-8266565: Spec of ForwardingJavaFileManager/ForwardingFileObjectorwardingJavaFileObject methods should mention delegation instead of being copied

[Jonathan Gibbons]

Please review a simple doc-only clarification to the spec for the `Forwarding...` classes in `javax.tools`.

The change is as in the CSR.

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Commit messages:
 - JDK-8266565: Spec of ForwardingJavaFileManager/ForwardingFileObject/ForwardingJavaFileObject methods should mention delegation instead of being copied

Changes: https://git.openjdk.java.net/jdk/pull/4735/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4735&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266565
  Stats: 11 lines in 3 files changed: 9 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4735.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4735/head:pull/4735

PR: https://git.openjdk.java.net/jdk/pull/4735