RFR: 8257799: Update JLS cross-references in java.compiler

[Joe Darcy]

A few of the @jls tags in the java.compiler module don't make the corresponding JLS section anymore; the null literal section and constant expression sections were renumbered.

This change makes corrects the mismatches.

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Commit messages:
 - JDK-8257799

Changes: https://git.openjdk.java.net/jdk/pull/1642/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1642&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257799
  Stats: 3 lines in 2 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1642.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1642/head:pull/1642

PR: https://git.openjdk.java.net/jdk/pull/1642