docs: clarifies setColour method signature

Author: Genyus

README.md

@@ -25,7 +25,7 @@ Inside the `com.cbfacademy.cars` package under the `cars` module, create a class
 - `public String getModel()` - returns the car model
 - `public int getYear()` - returns the year the car was made
 - `public String getColour()` - returns the colour of the car
-- `public void setColour()` - sets the colour of the car
+- `public void setColour(String colour)` - sets the colour of the car
 - `public String getDetails()` - returns the car details, including the make, model, colour and year
 
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