Mark QNmeaPositionInfoSource tests as insignificant on Windows.

The local TCP socket required by these tests regularly fails on the
Windows CI due to heavy load.

Change-Id: I65e6150b8c735aec85e643cf1702344ff707723d
Reviewed-by: Aaron McCarthy <mccarthy.aaron@gmail.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>