RFR: 8375683: Add notes for sctp tests [v2]

[SendaoYan]

> Hi all,
> 
> The sctp tests need libsctp.so to be installed, otherwise those tests will report skipped. Seems that there is no help information to descripte how to run those tests. I think it's meaningful to add help information how to run those tests.

SendaoYan has updated the pull request incrementally with one additional commit since the last revision:

  Update the testing.html through "make update-build-docs"

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Changes:
  - all: https://git.openjdk.org/jdk/pull/29320/files
  - new: https://git.openjdk.org/jdk/pull/29320/files/938932f2..0182358f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29320&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29320&range=00-01

  Stats: 11 lines in 1 file changed: 11 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/29320.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29320/head:pull/29320

PR: https://git.openjdk.org/jdk/pull/29320