Correct formatting in README.md

Author: neil.hamilton

README.md

@@ -65,7 +65,7 @@ The following drivers and devices are not yet supported:
 * `plcm3` - PicoLog CM3 Current Data Logger
 * `ps3000` - PicoScope 3204, 3205, 3206, 3223, 3224, 3423 & 3423
 * `usbpt104` - PT-104 Platinum Resistance Data Logger
-* `ps6000a - PicoScope 6804E & 6824E
+* `ps6000a` - PicoScope 6804E & 6824E
 
 ### Dependencies