Avoid using uppercase text-transform (#12684)

One user suggested that the loading indicator should not be written
ALL CAPS, at first it was thought this change is very minor, but then
a few other people asked agreed on the same thing - variant without
caps looks better. It may be related that it is harder to read or just
looks too "catchy". Moreover, I asked @rf@mastodonsocial.ru community
what they think of that and 82% of 22 people agreed on this change.

This commit removes all usage of text-transform: uppercase, where the
font size specified, it changes the value by one pixel larger, so we
still keeping the "designed" size of the labels but without using CAPS.