MAINTAINERS: update st,hts221.yaml reference

Changeset 9a6ac313 ("dt-bindings:iio:humidity:st,hts221 yaml conversion.")
renamed: Documentation/devicetree/bindings/iio/humidity/hts221.txt
to: Documentation/devicetree/bindings/iio/humidity/st,hts221.yaml.

Update its cross-reference accordingly.

Fixes: 9a6ac313 ("dt-bindings:iio:humidity:st,hts221 yaml conversion.")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

MAINTAINERS

@@ -8209,7 +8209,7 @@ M:	Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
 L:	linux-iio@vger.kernel.org
 S:	Maintained
 W:	http://www.st.com/
-F:	Documentation/devicetree/bindings/iio/humidity/hts221.txt
+F:	Documentation/devicetree/bindings/iio/humidity/st,hts221.yaml
 F:	drivers/iio/humidity/hts221*
 
 HUAWEI ETHERNET DRIVER