[jdk17u-dev] RFR: 8286573: Remove the unnecessary method Attr#attribTopLevel and its usage

[Guoxiong Li]

Hi all,

Request to backport this change to jdk17. The code applies cleanly.

Low risk: just clean some unnecessary code and trivial change.

Best Regard,
-- Guoxiong

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Commit messages:
 - Backport 36bdd25159ff78425e5f0a1145a814d9edca97ae

Changes: https://git.openjdk.org/jdk17u-dev/pull/544/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=544&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8286573
  Stats: 16 lines in 1 file changed: 0 ins; 16 del; 0 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/544.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev pull/544/head:pull/544

PR: https://git.openjdk.org/jdk17u-dev/pull/544