docs: Fix formatting of DAC code examples.

docs/library/pyb.DAC.rst

@@ -26,11 +26,11 @@ To output a continuous sine-wave::
     # create a buffer containing a sine-wave
     buf = bytearray(100)
     for i in range(len(buf)):
-        buf[i] = 128 + int(127 \* math.sin(2 \* math.pi \* i / len(buf)))
+        buf[i] = 128 + int(127 * math.sin(2 * math.pi * i / len(buf)))
 
     # output the sine-wave at 400Hz
     dac = DAC(1)
-    dac.write_timed(buf, 400 \* len(buf), mode=DAC.CIRCULAR)
+    dac.write_timed(buf, 400 * len(buf), mode=DAC.CIRCULAR)
 
 To output a continuous sine-wave at 12-bit resolution::
 
@@ -43,7 +43,7 @@ To output a continuous sine-wave at 12-bit resolution::
 
     # output the sine-wave at 400Hz
     dac = DAC(1, bits=12)
-    dac.write_timed(buf, 400 \* len(buf), mode=DAC.CIRCULAR)
+    dac.write_timed(buf, 400 * len(buf), mode=DAC.CIRCULAR)
 
 Constructors
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