fix "type object 'gnuradio.filter.filter_python.firdes' has no attribute 'WIN_KAISER'" (another error blocks update of fm_radio.py)

fm_radio.grc

@@ -179,7 +179,7 @@ blocks:
     samp_rate: samp_rate
     type: fir_filter_ccf
     width: '10000'
-    win: firdes.WIN_KAISER
+    win: window.WIN_KAISER
   states:
     bus_sink: false
     bus_source: false