docs: fix spelling errors for amount in retry (#69)

Fixes #68

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Fixes #68

google/api_core/retry.py

@@ -125,9 +125,9 @@ def exponential_sleep_generator(initial, maximum, multiplier=_DEFAULT_DELAY_MULT
         https://cloud.google.com/storage/docs/exponential-backoff
 
     Args:
-        initial (float): The minimum amout of time to delay. This must
+        initial (float): The minimum amount of time to delay. This must
             be greater than 0.
-        maximum (float): The maximum amout of time to delay.
+        maximum (float): The maximum amount of time to delay.
         multiplier (float): The multiplier applied to the delay.
 
     Yields:
@@ -333,9 +333,9 @@ def with_delay(self, initial=None, maximum=None, multiplier=None):
         """Return a copy of this retry with the given delay options.
 
         Args:
-            initial (float): The minimum amout of time to delay. This must
+            initial (float): The minimum amount of time to delay. This must
                 be greater than 0.
-            maximum (float): The maximum amout of time to delay.
+            maximum (float): The maximum amount of time to delay.
             multiplier (float): The multiplier applied to the delay.
 
         Returns: