tests: Do not enable virtual device hot seconds under valgrind

Valgrind tests may be slow, leading the devices to be considered hot.

We don't disable this for other tests, since we may still want to be
sure that the logic is fine for normal usage

tests/meson.build

@@ -375,6 +375,8 @@ if valgrind.found()
         env: [
             'G_SLICE=always-malloc',
             'UNDER_VALGRIND=1',
+            'FP_VIRTUAL_IMAGE_HOT_SECONDS=-1',
+            'FP_VIRTUAL_DEVICE_HOT_SECONDS=-1',
             'LIBFPRINT_TEST_WRAPPER=' + ' '.join(libfprint_wrapper),
         ])
 endif