Remove duplicate/unused link attribute

(cherry picked from commit 19557e4)

Author: marcphilipp

documentation/src/docs/asciidoc/link-attributes.adoc

@@ -103,7 +103,6 @@ endif::[]
 :Events:                                     {javadoc-root}/org.junit.platform.testkit/org/junit/platform/testkit/engine/Events.html[Events]
 :EventStatistics:                            {javadoc-root}/org.junit.platform.testkit/org/junit/platform/testkit/engine/EventStatistics.html[EventStatistics]
 :EventType:                                  {javadoc-root}/org.junit.platform.testkit/org/junit/platform/testkit/engine/EventType.html[EventType]
-:Execution:                                  {javadoc-root}/org.junit.platform.testkit/org/junit/platform/testkit/engine/Execution.html[Execution]
 :Executions:                                 {javadoc-root}/org.junit.platform.testkit/org/junit/platform/testkit/engine/Executions.html[Executions]
 :TerminationInfo:                            {javadoc-root}/org.junit.platform.testkit/org/junit/platform/testkit/engine/TerminationInfo.html[TerminationInfo]
 :TestExecutionResultConditions:              {javadoc-root}/org.junit.platform.testkit/org/junit/platform/testkit/engine/TestExecutionResultConditions.html[TestExecutionResultConditions]