Suggested rewording of definition for band ogives

[andypbarrett]

The current definition is almost correct but is misleading because ogives always form below icefalls (Paterson, 1986).

1: Alternate bands of light and dark on a glacier; usually found below steep narrow
icefalls and thought to be the result of different flow and ablation rates between
summer and winter.

https://github.com/nsidc/nsidc_cryosphere_glossary/blob/5c1d18e0d6e8d59837e84d5904fe50bd3bc2b9d5/glossary/b/band_ogives.yml#L1C1-L5C23

Suggest

" Alternate bands of light and dark ice on a glacier surface found below icefalls that are thought to form because of differences in flow and ablation rates between summer and winter."