MAINTAINERS: drop the sensor area label from few ares

Drop the "area: Sensors" label from Wurth and TDK sensor areas, the
current setup is causing the issue assigner script to pick up those
maintainers for any issue labeled as sensor as it does not know better,
if these areas wants a label for issue tracking their maintainer can
make an area specific one and use it.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>