adding V3 N/A label instructions

Signed-off-by: anaxceron <[email protected]>

.github/pr-comments/for-labeller.md

@@ -3,6 +3,7 @@
 - [ ] Add the label `review: doc`.
 - [ ] Identify your content topic with a label. (Examples: `area: apiml`, `area: cli`, `area: install and config`, etc.)
 - [ ] Specify the major Zowe release(s) for your content. (Examples: `release: V1`, `release: V2`, `release: V3`)
+    - [ ] If adding content that needs to be removed from V3 documentation, add the `V3 N/A` tag.
 - [ ] Select the `master` branch if your PR updates content that is on the **live site**. Select `docs-staging` if your PR updates content for a future release.
 - [ ] Notify the Doc Squad about this PR. If you don't know whom should review your content, message the [#zowe-doc](https://openmainframeproject.slack.com/archives/CC961JYMQ) Slack channel. If you know which Doc Squad writer should approve your content, add that person as a reviewer.
 

.github/pr-comments/for-writer.md

@@ -3,6 +3,7 @@
 - [ ] Add the label `review: sme` if an SME needs to check your content.
 - [ ] Identify your content topic with a label. (Examples: `area: apiml`, `area: cli`, `area: install and config`, etc.)
 - [ ] Specify the major Zowe release(s) for your content. (Examples: `release: V1`, `release: V2`, `release: V3`)
+    - [ ] If adding content that needs to be removed from V3 documentation, add the `V3 N/A` tag.
 - [ ] Link any [Doc Issues](https://github.com/zowe/docs-site/issues) related to this PR.
 - [ ] Fix broken links found in your content areas.
 - [ ] Notify the SME to review this PR (if applicable).