Try to better clean up test fixtures.

Author: Gary Gregory

src/test/java/org/apache/commons/io/input/MemoryMappedFileInputStreamTest.java

@@ -50,6 +50,13 @@ void afterEach() {
         // otherwise the temporary files won't be able to be removed when running on
         // Windows. Calling gc() is just a hint to the VM.
         System.gc();
+        Thread.yield();
+        System.runFinalization();
+        Thread.yield();
+        System.gc();
+        Thread.yield();
+        System.runFinalization();
+        Thread.yield();
     }
 
     private Path createTestFile(final int size) throws IOException {