Update variables_style_rules.csv

Author: RDaxini

pvlib/data/variables_style_rules.csv

@@ -11,7 +11,7 @@ ghi;global horizontal irradiance
 ghi_extra;horizontal irradiance at top of atmosphere (extraterrestrial)
 gri;ground-reflected irradiance
 ape;average photon energy
-aoi;angle of incidence between :math:`90\deg` and :math:`90\deg`
+aoi;angle of incidence between ±90°
 aoi_projection;cos(aoi)
 airmass;airmass
 airmass_relative;relative airmass