Fix code owners and pull request template (#200)

Author: alexshtin

.github/CODEOWNERS

@@ -1,4 +1,5 @@
 # Syntax is here:
 # https://docs.github.com/en/github/creating-cloning-and-archiving-repositories/about-code-owners#codeowners-syntax
 
-*                @temporalio/core
+*                @temporalio/server
+*                @temporalio/sdk

.github/PULL_REQUEST_TEMPLATE.md

@@ -6,10 +6,6 @@
 **Why?**
 
 
-<!-- How have you verified this change? Tested locally? Added a unit test? Checked in staging env? -->
-**How did you test it?**
-
-
-<!-- Assuming the worst case, what can be broken when deploying this change to production? -->
-**Potential risks**
+<!-- Are there any breaking changes on binary or code level? -->
+**Breaking changes**