[jdk26] RFR: 8370970: DocCheck failure in jdkDoctypeBadcharsCheck.java and jdkCheckHtml.java

[Dan Smith]

This pull request contains a backport of commit [c16ce929](https://github.com/openjdk/jdk/commit/c16ce929c7bc127fe18d3faa037d81c2760a44a2) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.

The commit being backported was authored by Dan Smith on 17 Dec 2025 and was reviewed by Chen Liang.

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Commit messages:
 - Backport c16ce929c7bc127fe18d3faa037d81c2760a44a2

Changes: https://git.openjdk.org/jdk/pull/28881/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28881&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370970
  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/28881.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28881/head:pull/28881

PR: https://git.openjdk.org/jdk/pull/28881