RFR: 8372938: Fix reference to DeferredStatic<T> in HotSpot Style Guide

[Kim Barrett]

Please review this trivial editorial fix to the HotSpot Style Guide.
JDK-8360458 changed the name of the utility class `Deferred<T>` to
`DeferredStatic<T>`, but forgot to update the reference to that class in the
Style Guide.

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Commit messages:
 - fix reference

Changes: https://git.openjdk.org/jdk/pull/28602/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28602&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8372938
  Stats: 3 lines in 2 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/28602.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28602/head:pull/28602

PR: https://git.openjdk.org/jdk/pull/28602