RFR: JDK-8300909: Update com/sun/jndi/dns/Test6991580.java manual test instruction [v2]

[Bill Huang]

> Test failed for exception in thread "main" java.lang.IllegalAccessError: class IPv6NameserverPlatformParsingTest (in unnamed module @0x72a8ab1a) cannot access class com.sun.jndi.dns.DnsContextFactory (in module jdk.naming.dns) because module jdk.naming.dns does not export com.sun.jndi.dns to unnamed module @0x72a8ab1a
> 	at IPv6NameserverPlatformParsingTest.main(IPv6NameserverPlatformParsingTest.java:46)
> 
> This task is created to update test instruction to include --add-modules and --add-opens jvm parameters to java command.

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

  Removed --add-modules.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12351/files
  - new: https://git.openjdk.org/jdk/pull/12351/files/d274657f..d271f3ba

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12351&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12351&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/12351.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12351/head:pull/12351

PR: https://git.openjdk.org/jdk/pull/12351