chore(sonar): don't use java 9 language

Author: oliemansm

graphql-spring-boot-autoconfigure/src/test/java/graphql/kickstart/autoconfigure/editor/voyager/VoyagerWithCsrfTest.java

@@ -34,7 +34,7 @@ void shouldLoadCSRFData() throws Exception {
         mockMvc.perform(get("/voyager")).andExpect(status().isOk()).andReturn();
 
     final Document document = Jsoup.parse(mvcResult.getResponse().getContentAsString());
-    var script = document.body().select("body script").dataNodes().get(0).getWholeData();
+    final String script = document.body().select("body script").dataNodes().get(0).getWholeData();
     assertThat(script)
         .contains("let csrf = {\"")
         .contains("\"token\":\"")

graphql-spring-boot-autoconfigure/src/test/java/graphql/kickstart/autoconfigure/editor/voyager/VoyagerWithoutCsrfTest.java

@@ -30,7 +30,7 @@ void shouldLoadCSRFData() throws Exception {
         mockMvc.perform(get("/voyager")).andExpect(status().isOk()).andReturn();
 
     final Document document = Jsoup.parse(mvcResult.getResponse().getContentAsString());
-    var script = document.body().select("body script").dataNodes().get(0).getWholeData();
+    final String script = document.body().select("body script").dataNodes().get(0).getWholeData();
     assertThat(script).contains("let csrf = null");
   }
 }