fix method rename error

Author: flavius-t

src/edgepi/adc/README.md

@@ -40,7 +40,7 @@ edgepi_adc.start_conversions()
 
 # perform 10 voltage reads
 for _ in range(10):
-  out = edgepi_adc.read_adc()
+  out = edgepi_adc.read_voltage()
   print(out)
   
 # stop automatic conversions

src/edgepi/dac/README.md

@@ -16,7 +16,7 @@ edgepi_dac = EdgePiDAC()
 edgepi_dac.write_voltage(1, 3.3)
 
 # read last voltage written to pin number 1
-edgepi_dac.read_adc(1)
+edgepi_dac.read_voltage(1)
 ```
 ---
 ## Using DAC Module

src/test_edgepi/integration_tests/test_adc/test_adc.py

@@ -814,7 +814,7 @@ def test_voltage_continuous(adc_num, ch, adc):
             )
         adc.start_conversions(adc_num)
         for _ in range(10):
-            out = adc.read_adc(adc_num)
+            out = adc.read_voltage(adc_num)
             assert out != 0
     finally:
         adc.stop_conversions(adc_num)