Remove deprecated siunitx options

The micro-related options were removed in major release 3:

https://github.com/josephwright/siunitx/blob/main/CHANGELOG.md#v300

There are two micro-signs relevant to us in Unicode:

U+00B5: µ (Micro sign)

U+03BC: μ (Greek letter mu)

See also https://tex.stackexchange.com/a/54915/120853 .

It's an annoying differentiation that is sometimes necessary,
*BUT* for now it seems the two important use cases of Mu work:

\si{\micro\gram} for units works (upright mu)

\(\mu\) works (slanted/italics math-mode mu)

Therefore, a user might never run into this issue/distinction.

Fixes #6

docker/tex/acp.cls

@@ -2559,8 +2559,6 @@
         % en-dash via '--', but inside \text{}, so it's not 'two minus signs'
         % range-phrase={\,\text{--}\,},
         range-units=single,% single: Print unit only once, at end
-        math-micro=\text{µ},% https://tex.stackexchange.com/a/54915/120853
-        text-micro=µ,
         per-mode=symbol,
         %
         binary-units, % Allow "GB" for gigabyte etc., which isn't strictly SI but useful