Update maven plugin (#12964)

### Summary
Now we need to upload to central portal instead of OSSRH
### Test plan
Example workflow:
https://github.com/pytorch/executorch/actions/runs/16602690475

Author: kirklandsign

extension/android/build.gradle

@@ -17,7 +17,7 @@ allprojects {
 
         dependencies {
             classpath 'com.android.tools.build:gradle:8.9.0'
-            classpath 'com.vanniktech:gradle-maven-publish-plugin:0.31.0'
+            classpath 'com.vanniktech:gradle-maven-publish-plugin:0.34.0'
         }
 
     }

extension/android/executorch_android/build.gradle

@@ -58,13 +58,11 @@ dependencies {
     androidTestImplementation 'org.jetbrains.kotlin:kotlin-test:1.9.23'
 }
 
-import com.vanniktech.maven.publish.SonatypeHost
-
 mavenPublishing {
-  publishToMavenCentral(SonatypeHost.DEFAULT)
+  publishToMavenCentral()
   signAllPublications()
 
-  coordinates("org.pytorch", "executorch-android", "0.7.0")
+  coordinates("org.pytorch", "executorch-android", "0.7.0-SNAPSHOT")
 
   pom {
     name = "ExecuTorch Android"
@@ -96,6 +94,6 @@ mavenPublishing {
 
 repositories {
     maven {
-        url "https://oss.sonatype.org/content/repositories/snapshots"
+        url "https://central.sonatype.com/repository/maven-snapshots/"
     }
 }