RFR: 8264866: Remove unneeded WorkArounds.isAutomaticModule

[Joe Darcy]

Simple cleanup as a follow-on to JDK-8264865. Clean langtools test run.

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Commit messages:
 - 8264866: Remove unneeded WorkArounds.isAutomaticModule

Changes: https://git.openjdk.java.net/jdk/pull/4417/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4417&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264866
  Stats: 13 lines in 2 files changed: 0 ins; 12 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4417.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4417/head:pull/4417

PR: https://git.openjdk.java.net/jdk/pull/4417