RFR: 8339236: Suppress removal warnings for Security Manager methods in iOS sources

[Jose Pereda]

This PR adds the required annotations to the iOS sources in the JavaFX Web module, to allow the compilation of such sources, now that `-Werror` is enabled, in the same way that was done for https://bugs.openjdk.java.net/browse/JDK-8264139 (where it was already mentioned https://github.com/openjdk/jfx/pull/528#issue-910936512 the need of a follow-up for iOS/Android).

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Commit messages:
 - Add suppress warnings to iOS sources

Changes: https://git.openjdk.org/jfx/pull/1550/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1550&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339236
  Stats: 14 lines in 4 files changed: 11 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jfx/pull/1550.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1550/head:pull/1550

PR: https://git.openjdk.org/jfx/pull/1550