RFR: 8331331: :tier1 target explanation in doc/testing.md is incorrect

[SendaoYan]

Hi,

In doc/testing.md file, it says:

As an example, :tier1 will expand to jtreg:$(TOPDIR)/test/hotspot/jtreg:tier1 jtreg:$(TOPDIR)/test/jdk:tier1 jtreg:$(TOPDIR)/test/langtools:tier1 jtreg:$(TOPDIR)/test/nashorn:tier1 jtreg:$(TOPDIR)/test/jaxp:tier1.

The actual situation is :tier1 doesn't contains test/nashorn:tier1, and the document missed test/lib-test:tier1

$ make -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'

Only change the document, no risk.

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Commit messages:
 - 8331331 :tier1 target explanation in doc/testing.md is incorrect

Changes: https://git.openjdk.org/jdk/pull/19002/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19002&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331331
  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/19002.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19002/head:pull/19002

PR: https://git.openjdk.org/jdk/pull/19002