Fix snippets typos

snippets/uniqueElementsByRight.md

@@ -2,7 +2,7 @@
 
 Returns all unique values of an array, based on a provided comparator function.
 
-Use `Array.prototype.reduce()` and `Array.prototype.some()` for an array containing only the last unique occurence of each value, based on the comparator function, `fn`.
+Use `Array.prototype.reduce()` and `Array.prototype.some()` for an array containing only the last unique occurrence of each value, based on the comparator function, `fn`.
 The comparator function takes two arguments: the values of the two elements being compared.
 
 ```js