Sjavac test failes in langtools nightly

In JDK-8015145, I converted the test for sjavac into a jtreg test. This proved to be a mistake. Since sjavac isn't being shipped with the product, tests for it can't be included in the regression testsuite as they will not even compile when run against a product build.

I propose to remove the jtreg declaration from this test to make it stop failing.