Note deprecation of aggregate_timeseries key in documentation

[rHorsey]

Describe the bug
The aggregate_timeseries key in the postprocessing key has been deprecated (https://github.com/NREL/buildstockbatch/blob/develop/buildstockbatch/base.py#L332) but the documentation does not indicate this.

Expected behavior
Changelog note, removal from tests, deprecation note in the documentation of the schema and removal from the example schema.

Platform (please complete the following information):

• Simulation platform: All
• BuildStockBatch version, branch, or sha: Develop
• OpenStudio-BuildStock version, branch, or sha: N/A
• Local Desktop OS: N/A

[nmerket]

@rHorsey It's like you want us to actually maintain this software.

[vtnate]

Also remove it from the validation which still requires it.

[asparke2]

This issues was resolved by #228, as noted in changelog_dev.rst:

    .. change::
        :tags: postprocessing
        :pullreq: 228
        :tickets: 182

        Moves the ``eagle.postprocessing.keep_intermediate_files`` to
        ``postprocessing.keep_individual_timeseries`` and changes behavior to
        keep only the timeseries parquet files. Also, removes the deprecated
        ``aggregate_timeseries`` key as that aggregation always happens.