[lilliput-jdk17u:lilliput] Integrated: 8308641: [Lilliput/JDK17] Remove wrong assert in klass.hpp

[Roman Kennke]

In klass.hpp, Klass::prototype_header() we have an assert(UseCompactObjectHeaders) which came from the similar upstream jdk21 change, but is wrong in jdk17, because the prototype_header() will also be used when biased locking is used. Biased locking is disabled by default, and the assert is harmless in release builds, but it makes a bunch of tests fail. Let's remove the assert and reduce upstream-jdk17u diff a little bit.

Testing:
 - [x] tier1 on x86, where some tests failed before

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Commit messages:
 - 8308641: [Lilliput/JDK17] Remove wrong assert in klass.hpp

Changes: https://git.openjdk.org/lilliput-jdk17u/pull/23/files
 Webrev: https://webrevs.openjdk.org/?repo=lilliput-jdk17u&pr=23&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8308641
  Stats: 4 lines in 1 file changed: 0 ins; 3 del; 1 mod
  Patch: https://git.openjdk.org/lilliput-jdk17u/pull/23.diff
  Fetch: git fetch https://git.openjdk.org/lilliput-jdk17u.git pull/23/head:pull/23

PR: https://git.openjdk.org/lilliput-jdk17u/pull/23