update documentation in some places (#844)

Author: hhanesand

Parse/PFAnalytics.h

@@ -142,7 +142,7 @@ NS_ASSUME_NONNULL_BEGIN
  store a data point at the time of invocation with the given event name. The
  event will be sent at some unspecified time in the future, even if Parse is currently inaccessible.
 
- @discussionDimensions will allow segmentation of the occurrences of this custom event.
+ @discussion Dimensions will allow segmentation of the occurrences of this custom event.
  Keys and values should be NSStrings, and will throw otherwise.
 
  To track a user signup along with additional metadata, consider the following:

Parse/PFObject.h

@@ -241,7 +241,7 @@ NS_REQUIRES_PROPERTY_DEFINITIONS
  Adds the objects contained in another array to the array associated with a given key,
  only adding elements which are not already present in the array.
 
- @dicsussion The position of the insert is not guaranteed.
+ @discussion The position of the insert is not guaranteed.
 
  @param objects The array of objects to add.
  @param key The key.