modernize-spelling: lowercase street arab

[robinwhittleton]

We still want to drop the hyphen though. It should also work in the plural.

In the corpus there’s “street Arab” with a capital in the following productions that I’ll fix:

• alexandre-dumas_the-count-of-monte-cristo_chapman-and-hall
• arthur-conan-doyle_a-study-in-scarlet
• arthur-conan-doyle_the-memoirs-of-sherlock-holmes
• arthur-conan-doyle_the-sign-of-the-four
• d-h-lawrence_women-in-love
• emile-gaboriau_monsieur-lecoq_laura-e-kendall
• emile-gaboriau_the-slaves-of-paris_charles-scribners-sons
• erskine-childers_the-riddle-of-the-sands
• ethel-voynich_the-gadfly
• fergus-hume_the-mystery-of-a-hansom-cab
• freeman-wills-crofts_the-cask
• honore-de-balzac_father-goriot_ellen-marriage
• honore-de-balzac_shorts-from-scenes-from-private-life_clara-bell_ellen-marriage
• israel-zangwill_the-big-bow-mystery
• jack-london_the-iron-heel
• kate-chopin_short-fiction
• l-m-montgomery_anne-of-green-gables
• marcel-proust_in-search-of-lost-time_c-k-scott-moncrieff
• maurice-leblanc_the-crystal-stopper_alexander-teixeira-de-mattos
• maurice-leblanc_the-secret-tomb_alexander-teixeira-de-mattos
• sigfrid-siwertz_downstream_e-classen
• victor-hugo_les-miserables_isabel-f-hapgood

Fixes #771.

[acabal]

Thanks!