Remove duplicate Helper call

The testRustContext function is used to prepare the environment for the
unit tests. As such, it is marked as a Helper function. Remove a
second superfluous call within its definition.

Test: m nothing
Change-Id: I37ea9a584b33498794c1cac828a7557d4bea8d7c

rust/rust_test.go

@@ -93,7 +93,6 @@ func testRustContext(t *testing.T, bp string, coverage bool) *android.TestContex
 		config.TestProductVariables.NativeCoveragePaths = []string{"*"}
 	}
 
-	t.Helper()
 	ctx := CreateTestContext()
 	ctx.Register(config)