Fix MockMvc sample setup

See gh-29201

src/docs/asciidoc/testing.adoc

@@ -7052,7 +7052,7 @@ To set up MockMvc through Spring configuration, use the following:
 
 		@BeforeEach
 		void setup(WebApplicationContext wac) {
-			this.mockMvc = MockMvcBuilders.webAppContextSetup(this.wac).build();
+			this.mockMvc = MockMvcBuilders.webAppContextSetup(wac).build();
 		}
 
 		// ...