Polish ExtendWith Docs

Use spring-framework-reference-url placeholder

Issue gh-10934

docs/modules/ROOT/pages/servlet/test/method.adoc

@@ -67,7 +67,7 @@ class WithMockUserTests {
     // ...
 }
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-<1> `@ExtendWith` instructs the spring-test module that it should create an `ApplicationContext`. For additional information refer to https://docs.spring.io/spring-framework/docs/current/reference/html/testing.html#testcontext-junit-jupiter-extension[Spring reference].
+<1> `@ExtendWith` instructs the spring-test module that it should create an `ApplicationContext`. For additional information, refer to the {spring-framework-reference-url}testing.html#testcontext-junit-jupiter-extension[Spring reference].
 <2> `@ContextConfiguration` instructs the spring-test the configuration to use to create the `ApplicationContext`. Since no configuration is specified, the default configuration locations will be tried. This is no different than using the existing Spring Test support. For additional information, refer to the https://docs.spring.io/spring-framework/docs/4.0.x/spring-framework-reference/htmlsingle/#testcontext-ctx-management[Spring Reference]
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