doctest fix for #42670 (whitespace removal)

Author: KrishnaSai2020

pandas/io/formats/format.py

@@ -1958,7 +1958,7 @@ def __call__(self, num: int | float) -> int:
         representing the power of 1000 of the original number. Some examples:
         >>> format_eng = EngFormatter()
         >>> format_eng(0)       # for self.accuracy = 0
-        ' 0'
+        '0'
 
         >>> format_eng(1000000) # for self.accuracy = 1,
                                 #     self.use_eng_prefix = True