Battery - CSS tweaks for consistency

[nicolethoen]

• Currently using a disabled color var for the default fill. maybe that's ok? maybe there is a more appropriate color. currently color fails contrast a11y on a white background.
• using an orange palette color for "high". probably ok, but ideally we would use a var we have... not sure if we have something between warning and error/danger though.
• Using #969696 for the stroke/outline. It's fine, it just isn't in our palette and a hex value is fixed, so it'll stay that color in different themes unless it's changed manually. We have a secondary border color that is almost identical. It's --pf-v5-global--BorderColor--200 and value is #8a8d90. Could we use our primary border color (--pf-v5-global--BorderColor--100)?