fix doc errors

Author: gfwilliams

libs/graphics/jswrap_graphics.c

@@ -2391,7 +2391,7 @@ JsVarInt jswrap_graphics_stringWidth(JsVar *parent, JsVar *var) {
 }
 Return the width and height in pixels of a string of text in the current font. The object returned contains:
 
-```JS
+```
 {
   width,              // Width of the string in pixels
   height,             // Height of the string in pixels

libs/puckjs/jswrap_puck.c

@@ -709,7 +709,7 @@ Check out [the Puck.js page on the
 magnetometer](http://www.espruino.com/Puck.js#on-board-peripherals) for more
 information.
 
-```JS
+```
 Puck.magOn(10); // 10 Hz
 Puck.on('mag', function(e) {
   print(e);
@@ -731,7 +731,7 @@ Called after `Puck.accelOn()` every time accelerometer data is sampled. There is
 one argument which is an object of the form `{acc:{x,y,z}, gyro:{x,y,z}}`
 containing the data.
 
-```JS
+```
 Puck.accelOn(12.5); // default 12.5Hz
 Puck.on('accel', function(e) {
   print(e);

src/jswrap_waveform.c

@@ -170,7 +170,7 @@ double-buffered - see `options` below) which contains the data to input/output.
 
 Options can contain:
 
-```JS
+```
 {
   doubleBuffer : bool   // whether to allocate two buffers or not (default false)
   bits         : 8/16   // the amount of bits to use (default 8).
@@ -181,7 +181,7 @@ When double-buffered, a 'buffer' event will be emitted each time a buffer is
 finished with (the argument is that buffer). When the recording stops, a
 'finish' event will be emitted (with the first argument as the buffer).
 
-```JS
+```
 // Output a sine wave
 var w = new Waveform(1000);
 for (var i=0;i<1000;i++) w.buffer[i]=128+120*Math.sin(i/2);
@@ -190,7 +190,7 @@ w.on("finish", () => print("Done!"))
 w.startOutput(H0,8000); // start playback
 ```
 
-```JS
+```
 // On 2v25, from Storage
 var f = require("Storage").read("sound.pcm");
 var w = new Waveform(E.toArrayBuffer(f));