Fix grammatical error in omega notation section

ruby/computer_science/time_complexity.md

@@ -231,7 +231,7 @@ If Big O gives us the worst-case scenario of how our algorithm will scale, what
 
 #### Big Ω (omega notation)
 
-Omega Notations gives us the best-case scenario for an algorithm. To understand where this might be, let's look at a method and discuss how we can measure its complexity.
+Omega Notation gives us the best-case scenario for an algorithm. To understand where this might be, let's look at a method and discuss how we can measure its complexity.
 
 ```ruby
 def find_value(arr)