RFR: 8318028: Remove unused class="centered" from FocusCycle.svg

[Alexey Ivanov]

**Cleanup**

A trivial modification which removes `class="centered"` from one of the `<text>` elements. It's a remnant from a previous version of the image.

Classes aren't used, all `<text>` elements are centered.

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Commit messages:
 - 8318028: Remove unused class="centered" from FocusCycle.svg

Changes: https://git.openjdk.org/jdk/pull/16168/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16168&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318028
  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16168.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16168/head:pull/16168

PR: https://git.openjdk.org/jdk/pull/16168