RFR: JDK-8289775: Update java.lang.invoke.MethodHandle[s] to use snippets

[Joe Darcy]

Update existing examples in  java.lang.invoke.{MethodHandle, MethodHandles} to use snippets rather than the older markup idiom.

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Commit messages:
 - JDK-8289775: Update java.lang.invoke.MethodHandle[s] to use snippets

Changes: https://git.openjdk.org/jdk/pull/9385/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9385&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289775
  Stats: 123 lines in 2 files changed: 0 ins; 1 del; 122 mod
  Patch: https://git.openjdk.org/jdk/pull/9385.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9385/head:pull/9385

PR: https://git.openjdk.org/jdk/pull/9385