meta: fix default labels of issue templates (#2191)

Author: Flash0ver

.github/ISSUE_TEMPLATE/bug.md

@@ -1,7 +1,7 @@
 ---
 name: 🐞 Bug Report
 about: Report a bug in this repo
-labels: ["Platform: Unity", "Type: Bug"]
+labels: ["Unity", "Bug"]
 ---
 
 ### Environment

.github/ISSUE_TEMPLATE/feature.md

@@ -1,7 +1,7 @@
 ---
 name: 💡 Feature Request
 about: Tell us about a problem our SDK could solve but doesn't.
-labels: ["Platform: Unity", "Type: Feature Request"]
+labels: ["Unity", "Feature"]
 ---
 
 What problem could Sentry solve that it doesn't?