RFR: 8304802: After JDK-8297639 the flag UsePreventiveGC needs to be added to the obsoletion table

[Thomas Schatzl]

Hi all,

  please review this change that puts the `G1UsePreventiveGC` into the argument obsoletion table so that the appropriate warning is printed when starting the VM with that option. Functionality has already been removed, and CSR request approved with [JDK-8297639](https://bugs.openjdk.org/browse/JDK-8297639).

Testing: local compilation, manual testing that the obsoletion warning is printed on the command line.

Thanks,
  Thomas

-------------

Commit messages:
 - initial version

Changes: https://git.openjdk.org/jdk/pull/13156/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13156&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8304802
  Stats: 9 lines in 2 files changed: 1 ins; 5 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/13156.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13156/head:pull/13156

PR: https://git.openjdk.org/jdk/pull/13156