Update README.md

removing grammatical error

subjects/pick-omit/README.md

@@ -5,7 +5,7 @@
 Create a `pick` function that takes an object and a string or array of strings.
 This function returns a new object that contains only the key/value pairs, whose key matches with the string or a string in the array, from the object passed as an argument.
 
-Create a `omit` function that takes an object and a a string or array of strings.
+Create a `omit` function that takes an object and a string or array of strings.
 This function returns a new object that contains only the key/value pairs, whose key doesn't match with the string or a single string in the array, from the object passed as an argument.
 
 > Those functions are pure and must not modify the given object