RFR: 8257038: Remove expired flags in JDK 18

[David Holmes]

Simple start of release update:
 - remove 4 expired flags
 - move the now obsoleted flags to the obsoleted flag section
 - update the dummy obsoleted flag

None of the expired flags were documented so no updated needed to any docs in that regard.

Thanks,
David

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Commit messages:
 - 8257038: Remove expired flags in JDK 18

Changes: https://git.openjdk.java.net/jdk/pull/4470/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4470&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257038
  Stats: 17 lines in 1 file changed: 5 ins; 9 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4470.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4470/head:pull/4470

PR: https://git.openjdk.java.net/jdk/pull/4470