Add note about failing test when using shared-mime-info < 1.0

Change-Id: I3ba9d14d915a579b9e102114866f6c9e0344ba16
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>

tests/auto/corelib/mimetypes/qmimedatabase/tst_qmimedatabase.cpp

@@ -721,6 +721,9 @@ void tst_QMimeDatabase::findByFile_data()
     findByFileName_data();
 }
 
+// Note: this test fails on "testcompress.z" when using a shared-mime-info older than 1.0.
+// This because of commit 0f9a506069c in shared-mime-info, which fixed the writing of
+// case-insensitive patterns into mime.cache.
 void tst_QMimeDatabase::findByFile()
 {
     QFETCH(QString, filePath);