[jdk16u] RFR: 8266288: assert root method not found in witnessed_reabstraction_in_supers is too strong

[Martin Doerr]

8266288: assert root method not found in witnessed_reabstraction_in_supers is too strong

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Commit messages:
 - Backport 49d04586ed27fc905083d60aa68793d84824c7f3

Changes: https://git.openjdk.java.net/jdk16u/pull/112/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk16u&pr=112&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266288
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk16u/pull/112.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16u pull/112/head:pull/112

PR: https://git.openjdk.java.net/jdk16u/pull/112