Add missing tests for Array#lastIndexOf (#1642)

Author: saulecabrera

NOTICE

@@ -31,6 +31,7 @@ under the licensing terms detailed in LICENSE:
 * Martin Fredriksson <martin.fredriksson@vikinganalytics.se>
 * forcepusher <bionitsoup@gmail.com>
 * Piotr Oleś <piotrek.oles@gmail.com>
+* Saúl Cabrera <saulecabrera@gmail.com>
 
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