Remove download badges from README

[AdamRJensen]

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There are currently two download badges on the pvlib python README page:

The first badge is from PyPi and the second from conda forge. Both badges show approximately the same number of downloads, but the first is per month and the second is totals - that seems inconsistent although I realize that they're different sources. I simply suggest to declutter the badge section and remove this downloads as they are dominated by automated tests downloading the packages and doesn't add any meaningful information/value (i.e., they say nothing about our actual user base).

There are already badges for both PyPi and conda forge at the top of the bad section in the "Latest release" section.

[kandersolar]

OK with me.

Tangentially related: can we updated all the conda-forge links in the first row to use pvlib instead of pvlib-python? The latter is just for backwards compatibility, so better to direct people to the former.