Remove unnecessary test task dependency (#76938)

We auto-wire the bwcTestSnapshots task to the check task. This dependOn
means we run the full wire compatible test suite on every build which
is not what we want since we run those explicitly in parallel CI jobs.
Running check should only test unreleased versions.

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

x-pack/plugin/sql/qa/mixed-node/build.gradle

@@ -62,9 +62,4 @@ for (Version bwcVersion : BuildParams.bwcVersions.wireCompatible.findAll { it.on
   tasks.register(bwcTaskName(bwcVersion)) {
     dependsOn "${baseName}#mixedClusterTest"
   }
-
-  // run these bwc tests as part of the "check" task
-  tasks.named("check").configure {
-    dependsOn "${baseName}#mixedClusterTest"
-  }
 }