Remove hardcoded secrets and improve CI configuration

Replaced hardcoded secrets access with dynamic property checks to
enhance security. Deleted unnecessary scripts and configurations for
handling secrets, streamlining the build process.

customtabs/build.gradle.kts

@@ -139,14 +139,16 @@ publishing {
         }
     }
 
-    repositories {
-        maven {
-            name = "sonatype"
-            credentials {
-                username = Secrets.Sonatype.user
-                password = Secrets.Sonatype.apiKey
+    if (hasProperty("sonatypeUser") && hasProperty("sonatypePass")) {
+        repositories {
+            maven {
+                name = "sonatype"
+                credentials {
+                    username = property("sonatypeUser") as String
+                    password = property("sonatypePass") as String
+                }
+                url = uri("https://oss.sonatype.org/service/local/staging/deploy/maven2")
             }
-            url = uri("https://oss.sonatype.org/service/local/staging/deploy/maven2")
         }
     }
 }