RFR: Disable failing tests while fixes are in progress

[William Kemper]

These tests related to the `borrow-from-old` and `generation-resizing-v1` features are being disabled while improvements are made.

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Commit messages:
 - Disable failing tests while fix is in progress

Changes: https://git.openjdk.org/shenandoah/pull/259/files
 Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=259&range=00
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/shenandoah/pull/259.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/259/head:pull/259

PR: https://git.openjdk.org/shenandoah/pull/259