meta: fix default labels of issue templates (#4270)

* meta: fix default labels of issue templates

* meta: change default label of Feature Request

Author: Flash0ver

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -1,6 +1,6 @@
 name: 🐞 Bug Report
 description: Tell us about something that's not working the way we (probably) intend.
-labels: ["Platform: .NET", "bug"]
+labels: [".NET", "Bug"]
 body:
   - type: dropdown
     id: nuget

.github/ISSUE_TEMPLATE/feature.yml

@@ -1,6 +1,6 @@
 name: 💡 Feature Request
 description: Tell us about a problem our SDK could solve but doesn't.
-labels: ["Platform: .NET", "enhancement"]
+labels: [".NET", "Feature"]
 body:
   - type: textarea
     id: problem