Fix typo in DDA algorithm description

Corrected a typo in the comment regarding the DDA algorithm.

Author: cclauss

graphics/digital_differential_analyzer_line.py

@@ -21,7 +21,7 @@ def digital_differential_analyzer_line(
     Despite this, DDA is useful for educational purposes as it is simple
     to understand and demonstrates the basic idea of incremental line generation.
 
-    This algorithm works by calculating the dx (change in x) and dy;(change in y) and
+    This algorithm works by calculating the dx (change in x) and dy (change in y) and
     then iteratively steps along the dominant axis, incrementing the other axis by a
     fractional amount (the slope).
     It is notable for its simplicity but also for its main disadvantage: