RFR: 8344534: Remove leftover import of java.security.AccessControlContext in JavaLangAccess

[Eirik Bjørsnøs]

Please review this trivial cleanup of an unused import of `AccessControlContext ` in `JavaLangAccess`. 

This was left over after #22035 removed `JavaLangAccess::newThreadWithAcc(Runnable, AccessControlContext)`.

Verification: `make images` succeeds.

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Commit messages:
 - Remove leftover import of JavaLangAccess

Changes: https://git.openjdk.org/jdk/pull/22234/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22234&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344534
  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/22234.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22234/head:pull/22234

PR: https://git.openjdk.org/jdk/pull/22234