[github] Update issue templates and cleanup old files

Closes: #236

.github/ISSUE_TEMPLATE/bug_report.md

@@ -32,7 +32,7 @@ To report a security issue, please email [email protected]. -->
 ## System information
 
 **Please complete the following information:**
-- <!-- Diem Version -->
+- <!-- Aptos Core Version -->
 - <!-- Rust Version -->
 - <!-- Computer OS -->
 

.github/ISSUE_TEMPLATE/documentation_bug_report.md

@@ -1,6 +1,6 @@
 ---
 name: "\U0001F41B Documentation/aptos.dev Bug report"
-about: Create a bug report to help improve the Diem Developers' Website
+about: Create a bug report to help improve the Aptos Developers' Website
 title: "[Bug]"
 labels: bug
 assignees: ''

.github/ISSUE_TEMPLATE/questions.md

@@ -1,10 +1,10 @@
 ---
 name: ❓ Questions/Help
-about: If you have questions, please check Discourse
+about: If you have questions, please check Discord
 ---
 
 ## ❓ Questions and Help
 
 ### Please note that this issue tracker is not a help form and this issue will be closed.
 
-Please contact the development team on [Discourse](https://community.libra.org)
+Please contact the development team on [Discord](https://discord.gg/gEV3C5jSnw)

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,5 +1,5 @@
 <!--
-Thank you for sending a PR. We appreciate you spending time to help improve the Diem project.
+Thank you for sending a PR. We appreciate you spending time to help improve the Aptos Core project.
 
 The project is undergoing daily changes. Pull Requests will be reviewed and responded to as time permits.
 -->
@@ -24,5 +24,5 @@ The project is undergoing daily changes. Pull Requests will be reviewed and resp
 
  * Justification and breaking nature (who does it affect? validators, full nodes, tooling, operators, AOS, etc.)
  * Comprehensive test results that demonstrate the fix working and not breaking existing workflows.
- * Why we must have it for V1 launch.
+ * Why we must have it for the release.
  * What workarounds and alternative we have if we do not push the PR.

.github/dep-auditors.json

@@ -1,4 +1,3 @@
 [
-  "davidiw",
-  "mimoo"
+  "davidiw"
 ]