Fixing a small typo. (#252)

Author: slaFFik

README.md

@@ -176,7 +176,7 @@ One or more environment variables failed assertions: DATABASE_DSN is empty
 
 ### Integer Variables
 
-You might also need to ensure the the variable is of an integer value. You may do the following:
+You might also need to ensure that the variable is of an integer value. You may do the following:
 
 ```php
 $dotenv->required('FOO')->isInteger();