RFR: JDK-8266808: Search label still uses old search field id

[Hannes Wallnöfer]

Trivial change to fix value of `for` attribute in javadoc search label.

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Commit messages:
 - JDK-8266808: Search label still uses old search field id

Changes: https://git.openjdk.java.net/jdk/pull/3949/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3949&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266808
  Stats: 7 lines in 2 files changed: 2 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3949.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3949/head:pull/3949

PR: https://git.openjdk.java.net/jdk/pull/3949