Corrected specs for pslab.io/specifications

```diff
4-Channel up to 2MSPS Oscilloscope. Software selectable amplification stages :heavy_check_mark:
-12-bit Voltmeter with programmable gain. Input ranges from +/-10 mV to +/-16 V
+12-bit Voltmeter with programmable gain. Input ranges from +/-50 mV to +/-16 V
3x 12-bit Programmable voltage sources +/-3.3 V,+/-5V,0-3 V
12-bit Programmable current source. 0-3.3 mA
Supports Advanced Plugins/Add-on Modules.
4-Channel, 4 MHz, Logic Analyzer.
- 2x Sine/Triangular wave generators. 5 Hz to 5 KHz. Manual amplitude control for SI1.
+ 2x Sine/Triangular wave generators. 5 Hz to 5 KHz.
4x PWM generators. 15 nS resolution. Up to 8 MHz.
Capacitance Measurement. pF to uF range.
I2C, UART data buses for Accel/gyros/humidity/temperature modules etc.
```

Start at the pslab.io/specifications page named in the issue and compare the listed oscilloscope, voltmeter, waveform-generator, and related specifications with the supplied diff. Done means the page reflects the corrected voltage range and the revised waveform-generator description exactly.

Written by the indexing model from the issue text.