Rename global cache to fibonacci_cache for clarity

Author: sheetalkharab

Sprint-2/improve_with_caches/fibonacci/fibonacci.py

@@ -1,11 +1,11 @@
-cache = {}
+fibonacci_cache = {}
 
 def fibonacci(n):
-    if(n) in cache:
-        return cache[n]
+    if(n) in fibonacci_cache:
+        return fibonacci_cache[n]
     if n <= 1:
         return n
 
     result = fibonacci(n - 1) + fibonacci(n - 2)
-    cache[n] = result 
+    fibonacci_cache[n] = result 
     return result