RFR: 8366543: Clean up include headers in numberSeq

[Albert Mingkun Yang]

Trivial changing to use the correct includes in `numberSeq.hpp/cpp`.

Test: tier1

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Commit messages:
 - num-seq-header

Changes: https://git.openjdk.org/jdk/pull/27031/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27031&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8366543
  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/27031.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27031/head:pull/27031

PR: https://git.openjdk.org/jdk/pull/27031