fix get_fee_text for static fees

mismatching units
probably only affects kivy gui; when using static fees

electrum/simple_config.py

@@ -403,11 +403,14 @@ class SimpleConfig(PrintError):
         """Returns (text, tooltip) where
         text is what we target: static fee / num blocks to confirm in / mempool depth
         tooltip is the corresponding estimate (e.g. num blocks for a static fee)
+
+        fee_rate is in sat/kbyte
         """
         if fee_rate is None:
             rate_str = 'unknown'
         else:
-            rate_str = format_fee_satoshis(fee_rate/1000) + ' sat/byte'
+            fee_rate = fee_rate/1000
+            rate_str = format_fee_satoshis(fee_rate) + ' sat/byte'
 
         if dyn:
             if mempool: