8133287: (fs) java/nio/file/Files/probeContentType/ParallelProbes.java should use othervm mode

Add @build tag containing ParallelProbes and SimpleFileTypeDetector and reinstate othervm mode.

Backport-of: eb790603374262134543bb03171a6ead1b13fc4b

Author: mrserb

jdk/test/java/nio/file/Files/probeContentType/ParallelProbes.java

@@ -29,7 +29,8 @@
 /* @test
  * @summary Test probing content type simultaneously from multiple threads.
  * @requires (os.family == "linux") | (os.family == "solaris")
- * @run main ParallelProbes 10
+ * @build ParallelProbes SimpleFileTypeDetector
+ * @run main/othervm ParallelProbes 10
  */
 public class ParallelProbes {