docs: pandas -> Pandas

[domoritz]

No description provided.

[mattijn]

When using the project name pandas, please use it in lower case, even at the beginning of a sentence.

See https://pandas.pydata.org/about/citing.html

[domoritz]

Today I learned. I always spelled it wrong then.

Note that this page has other mentions of pandas and spells it as "Pandas". So we will want to update those, right?

[mattijn]

Trying to give them the right credits.. I also think they deserve a capital p;).
I did a quick search and had 51 hits in the Altair docs where we use pandas with a capital p, so at least some of these require changing indeed..

[domoritz]

Thanks for making the changes. It looks odd to me as well but I prefer consistency over either option.