fix: Add maven-core to producer_with_git buildscript classpath

Same fix as producer_with_external_contracts - this module also uses
contractsMode = "LOCAL" and needs maven-core for SettingsDecryptionRequest.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: marcingrzejszczak

producer_with_git/build.gradle

@@ -1,3 +1,12 @@
+buildscript {
+	repositories {
+		mavenCentral()
+	}
+	dependencies {
+		classpath 'org.apache.maven:maven-core:3.9.6'
+	}
+}
+
 plugins {
 	id 'groovy'
 	id 'org.springframework.boot'