RFR: Fixed bugs in bug filing instructions [v2]

[Jesper Wilhelmsson]

> Changed to the correct address for filing vulnerabilities and added some clarifications.

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

  Clarified not to discuss vulnerabilities in the open

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

Changes:
  - all: https://git.openjdk.java.net/guide/pull/57/files
  - new: https://git.openjdk.java.net/guide/pull/57/files/25d2b888..8ecb9a48

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=guide&pr=57&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=guide&pr=57&range=00-01

  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/guide/pull/57.diff
  Fetch: git fetch https://git.openjdk.java.net/guide pull/57/head:pull/57

PR: https://git.openjdk.java.net/guide/pull/57