Disable LockTests.testReadWriteFileLock

[benlangmuir]

This test may fail spuriously if a reader thread runs before any writers
were able to write the initial value to the file. Disable the test until
it can be fixed. We saw the same issue with FileSystemTests in the past.

rdar://78461378

[benlangmuir]

@swift-ci please smoke test

[benlangmuir]

@tomerd FYI this looks like the same sort issue you fixed in #199, just in a different test.

[benlangmuir]

@swift-ci please test

[benlangmuir]

The Linux failure looks like a configuration issue unrelated to this PR:

11:22:36 error: could not decode frontend target info; compiler driver and frontend executables may be incompatible
11:22:36 details: frontend: /home/buildnode/jenkins/workspace/pr-swift-tools-support-core-linux/latest_toolchain/swift-5.3-RELEASE-ubuntu16.04/usr/bin/swift
11:22:36          arguments: ["-frontend", "-print-target-info", "-target", "x86_64-unknown-linux-gnu", "-sdk", "/home/buildnode/jenkins/workspace/pr-swift-tools-support-core-linux/branch-main/build/buildbot_incremental/swift-linux-x86_64/stdlib/public/core", "-resource-dir", "/home/buildnode/jenkins/workspace/pr-swift-tools-support-core-linux/branch-main/build/buildbot_incremental/swift-linux-x86_64/lib/swift", "-runtime-compatibility-version", "none"]
11:22:36          error: key missing: CodingKeys(stringValue: "compilerVersion", intValue: nil), path: []