[jdk17u-dev] RFR: 8331331: :tier1 target explanation in doc/testing.md is incorrect

[SendaoYan]

Hi,
  This is backport of [JDK-8331331](https://bugs.openjdk.org/browse/JDK-8331331). The `doc/testing.html` can not backport cleanly because of it's a prefixed patch [JDK-8295663](https://bugs.openjdk.org/browse/JDK-8295663).

$ make CONF=linux-x86_64-server-release -n test-tier1 &> test-tier1.log
$ grep "Running test " test-tier1.log
Running test 'jtreg:test/hotspot/jtreg:tier1'
Running test 'jtreg:test/jdk:tier1'
Running test 'jtreg:test/langtools:tier1'
Running test 'jtreg:test/jaxp:tier1'
Running test 'jtreg:test/lib-test:tier1'

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

Commit messages:
 - Backport 04271dfe7a262379944e2a2cf83a98a3a1b78a74

Changes: https://git.openjdk.org/jdk17u-dev/pull/2447/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=2447&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331331
  Stats: 6 lines in 2 files changed: 0 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/2447.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/2447/head:pull/2447

PR: https://git.openjdk.org/jdk17u-dev/pull/2447