[SMALLFIX] Fix Alluxio/new-contributor-tasks#638

[lucaspeng12138]

What changes are proposed in this pull request?

Change

alluxio/core/common/src/main/java/alluxio/conf/PropertyKey.java

Line 4193 in b9c66ca

.setAlias(new String[] {"alluxio.user.block.master.client.threads"})

from
.setAlias(new String[] {"alluxio.user.block.master.client.threads"})

to
.setAlias("alluxio.user.block.master.client.threads")

Why are the changes needed?

no need to use "new String"

Does this PR introduce any user facing changes?

Fixes Alluxio/Community#638

[alluxio-bot]

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[alluxio-bot]

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[lucaspeng12138]

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[alluxio-bot]

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