Fix section ID for parallel test execution

Issue: SPR-5863

Author: sbrannen

src/asciidoc/testing.adoc

@@ -3502,7 +3502,7 @@ be automatically rolled back by the `TransactionalTestExecutionListener` (see
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-[[testcontext-support-classes]]
+[[testcontext-parallel-test-execution]]
 ==== Parallel test execution
 
 Spring Framework 5.0 introduces basic support for executing tests in parallel within a