Fix minor typo

Changed the "three" to "four" in the beginning description of the processes in the README. This change was already made in the documentation.

README.md

@@ -9,7 +9,7 @@ in a text file.
 
 ## The Workflow
 
-The workflow `workflow/main.nf` has three processes:
+The workflow `workflow/main.nf` has four processes:
 
 - Convert all the text in the input files to uppercase
 - Split the text so each word is on a separate line