RFR: 8276880: Remove java/lang/RuntimeTests/exec/ExecWithDir as unnecessary

[Roger Riggs]

The java/lang/RuntimeTests/exec/ExecWithDir test forks 500 subprocesses hoping to trigger an intermittent problem fixed in 2002.

The test can be removed, it does not exercise the condition it was created for.

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Commit messages:
 - 8276880: Remove java/lang/RuntimeTests/exec/ExecWithDir as unnecessary

Changes: https://git.openjdk.java.net/jdk/pull/6318/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6318&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8276880
  Stats: 61 lines in 1 file changed: 0 ins; 61 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6318.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6318/head:pull/6318

PR: https://git.openjdk.java.net/jdk/pull/6318