chore: rename gcd to greatest_common_divisor (#6265)

As described in CONTRIBUTING.md

> Expand acronyms because gcd() is hard to understand but greatest_common_divisor() is not.

Co-authored-by: Dhruv Manilawala <[email protected]>

Author: ksharma20

project_euler/problem_005/sol2.py

@@ -16,28 +16,28 @@
 """
 
 
-def gcd(x: int, y: int) -> int:
+def greatest_common_divisor(x: int, y: int) -> int:
     """
-    Euclidean GCD algorithm (Greatest Common Divisor)
+    Euclidean Greatest Common Divisor algorithm
 
-    >>> gcd(0, 0)
+    >>> greatest_common_divisor(0, 0)
     0
-    >>> gcd(23, 42)
+    >>> greatest_common_divisor(23, 42)
     1
-    >>> gcd(15, 33)
+    >>> greatest_common_divisor(15, 33)
     3
-    >>> gcd(12345, 67890)
+    >>> greatest_common_divisor(12345, 67890)
     15
     """
 
-    return x if y == 0 else gcd(y, x % y)
+    return x if y == 0 else greatest_common_divisor(y, x % y)
 
 
 def lcm(x: int, y: int) -> int:
     """
     Least Common Multiple.
 
-    Using the property that lcm(a, b) * gcd(a, b) = a*b
+    Using the property that lcm(a, b) * greatest_common_divisor(a, b) = a*b
 
     >>> lcm(3, 15)
     15
@@ -49,7 +49,7 @@ def lcm(x: int, y: int) -> int:
     192
     """
 
-    return (x * y) // gcd(x, y)
+    return (x * y) // greatest_common_divisor(x, y)
 
 
 def solution(n: int = 20) -> int: