Fix typo in Taskkill in reaper (#61076)

The reaper is used only when spawned processes by the build like
testclusters or vagrant are left behind in a failed build. When this
occurs on Windows, the Taskkill command is used. However, there was a
typo in the command name. Since the reaper is for edgecases and mostly
protection for local builds (CI uses immutable hosts), this has been
broken since its inception.

closes #60503

buildSrc/src/main/java/org/elasticsearch/gradle/ReaperService.java

@@ -61,7 +61,7 @@ public class ReaperService {
      */
     public void registerPid(String serviceId, long pid) {
         String[] killPidCommand = OS.<String[]>conditional()
-            .onWindows(() -> new String[] { "Taskill", "/F", "/PID", String.valueOf(pid) })
+            .onWindows(() -> new String[] { "Taskkill", "/F", "/PID", String.valueOf(pid) })
             .onUnix(() -> new String[] { "kill", "-9", String.valueOf(pid) })
             .supply();
         registerCommand(serviceId, killPidCommand);