RFR: 8358035: Remove unused `compute_fingerprint` declaration in `ClassFileStream`

[Qizheng Xing]

In JDK-8264805 (part of JEP 410), the implementation of `compute_fingerprint` was removed from `ClassFileStream`, but its declaration was left in place, which was unused and should be removed. This patch removes that declaration.

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Commit messages:
 - Remove unused `compute_fingerprint` declaration in `ClassFileStream`

Changes: https://git.openjdk.org/jdk/pull/25518/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25518&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8358035
  Stats: 3 lines in 2 files changed: 0 ins; 3 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/25518.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25518/head:pull/25518

PR: https://git.openjdk.org/jdk/pull/25518