fix: tests may fail because of uncleared system property

GitHub Actions running on Unbuntu seems to be affected.

Author: BlasiusSecundus

graphql-kickstart-spring-boot-autoconfigure-tools/src/test/java/graphql/kickstart/tools/boot/GraphQLToolsDirectiveTest.java

@@ -4,6 +4,7 @@
 import graphql.schema.GraphQLObjectType;
 import graphql.schema.idl.SchemaDirectiveWiring;
 import graphql.schema.idl.SchemaDirectiveWiringEnvironment;
+import org.junit.After;
 import org.junit.Test;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -15,6 +16,11 @@ public GraphQLToolsDirectiveTest() {
     super(GraphQLJavaToolsAutoConfiguration.class);
   }
 
+  @After
+  public void clear() {
+    System.clearProperty("graphql.tools.schemaLocationPattern");
+  }
+
   @Test
   public void directiveIsLoaded() {
     System.setProperty("graphql.tools.schemaLocationPattern", "graphql/schema-directive-test.graphql");