blink LED while scanning leads to worse measurement

[qrp73]

blink LED while scanning leads to worse measurement due to voltage fluctuations and pulse interferences. This is because LED blinking leads to load change for the battery and voltage is jumping for a little. Also it leads to high frequency pulses at rise or fall moment and it leads to input interference.

Proposal: disable LED and don't blink during measurement cycle to avoid unwanted noise and power supply voltage fluctuations.

The fix is already done with this https://github.com/qrp73/NanoVNA-Q/commit/23dba7d9b4dce23889ec25e39c922cc9973daf82 and this https://github.com/qrp73/NanoVNA-Q/commit/3195ea0bd15fbc4dfdb71d0df15cb31f2591b296 changes