RFR: Fixed bugs in bug filing instructions [v4]

[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:

  Fixed discussion around access

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Changes:
  - all: https://git.openjdk.java.net/guide/pull/57/files
  - new: https://git.openjdk.java.net/guide/pull/57/files/e7f8e90c..2e9a10f8

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=guide&pr=57&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=guide&pr=57&range=02-03

  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 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