DOC: fix minor docstring grammar in events.py

[importstring]

This PR fixes a few small docstring grammar issues in ignite/engine/events.py. There are no code or behavior changes, only wording fixes in comments/docstrings.

All changes are minimal and localized, for example:

# Before
"""Single Event containing a filter, specifying whether the event should
be run at the current event (if the event type is correct)

Args:
    value: The actual enum value. Only needed for internal use. Do not touch!
    event_filter: A function taking the engine and the current event value as input and returning a
        boolean to indicate whether this event should be executed. Defaults to None, which will result to a
        function that always returns `True`
    name: The enum-name of the current object. Only needed for internal use. Do not touch!
"""

# After
"""Single event containing a filter specifying whether the handler should be run for the current event (if the event type is correct).

Args:
    value: The actual enum value. Only needed for internal use. Do not touch!
    event_filter: A function taking the engine and the current event value as input and returning a
        boolean to indicate whether this event should be executed. Defaults to None, which will result in a
        function that always returns `True`.
    name: The enum-name of the current object. Only needed for internal use. Do not touch!
"""

The deprecated default event filter docstring is also cleaned up: [is is]

# Before
"""Default event filter. This method is is deprecated and will be removed. Please, use None instead"""

# After
"""Default event filter. This method is deprecated and will be removed. Please use None instead."""

These changes:

• Fix a duplicated word: is is.
• Replace “result to” with the correct “result in”.
• Make the CallableEventWithFilter docstring clearer and grammatically correct.
• Fixed: "User can also combine events" --> "Users can also ..."

[vfdev-5]

Thanks

[aaishwarymishra]

@importstring Code style checks are failing pls try to use pre-commit hook :)

[importstring]

@aaishwarymishra Alright done. Let me know if this works!