Use standard var spelling for reactive power unit

[scop]

Description:

Note: this is a monkey change, I'm not 100% sure of the effects, please review with care. Home Assistant has switched from VAr to var a while back.

There are a few more occurrences of VAr in the tree, but changing those did not seem safe (or I was even more unsure what doing so might affect than the ones I included here).

• https://en.wikipedia.org/wiki/Volt-ampere#Volt-ampere_reactive
• https://engineering.electrical-equipment.org/energy-efficiency-kvar/kvar-or-kvar.html

Related issue (if applicable): fixes #

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.8
• The code change is tested and works with Tasmota core ESP32 V.3.1.0.241030
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass

[Jason2866]

There is a difference for
Unit name: Var
Unit symbol: var
regarding https://de.wikipedia.org/wiki/Var_(Einheit)
So imho leaving as it is.

[s-hadinger]

The international symbol is VA not va. I suggest that we stick to international official units.

Edit: hmmm. It seems that the international system actually switched to var.