MINOR: Preventing running the :core tests twice when testing with coverage (#15580)

reportScoverage task (which was used previously as dependency of the registered coverage task)
creates a task for each Test task and executes them. There's unitTest, integrationTest and
the test tasks (which is just for executing both unit and integration), so reportScoverage
executes all three with their corresponding scoverage task, hence running all tests twice.
Solution is just to use the reportTestScoverage task as dependency.

Reviewers: Viktor Somogyi-Vass <viktorsomogyi@gmail.com>

build.gradle

@@ -748,7 +748,7 @@ subprojects {
   }
 
   if (userEnableTestCoverage) {
-    def coverageGen = it.path == ':core' ? 'reportScoverage' : 'jacocoTestReport'
+    def coverageGen = it.path == ':core' ? 'reportTestScoverage' : 'jacocoTestReport'
     tasks.register('reportCoverage').configure { dependsOn(coverageGen) }
   }