Clean up 5.1 release notes and compat notes (#137)

Author: jeff-allen-mongo

source/release-notes/5.1-compatibility.txt

@@ -65,12 +65,6 @@ Aggregation
 
 .. include:: /includes/fact-5.1-setWindowFields-snapshot-restriction.rst
 
-Removed Index Types
--------------------
-
-Removed Metrics
----------------
-
 Replica Sets
 ------------
 
@@ -101,9 +95,6 @@ Time Series Collections
   Before downgrading to a version older than 5.0.4, drop all sharded
   time series collections.
 
-Auditing
---------
-
 General Changes
 ---------------
 
@@ -192,18 +183,6 @@ will receive an error message like the following:
    :: caused by :: network error while attempting to run command
    'isMaster' on host '127.0.0.1:27017'
 
-Deprecations
-------------
-
-.. list-table::
-   :widths: 20 80
-   :header-rows: 1
-
-   * - Deprecated
-     - Description
-   * - 
-     - 
-
 .. _5.1-compatibility-enabled:
 
 5.1 Feature Compatibility

source/release-notes/5.1.txt

@@ -104,9 +104,6 @@ $lookup and $graphLookup with sharded collections
 General Aggregation Improvements
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-:expression:`$dateSubtract` and :expression:`$dateAdd`: Improved Input Validation
-`````````````````````````````````````````````````````````````````````````````````
-
 Starting in MongoDB 5.1, :expression:`$dateSubtract` and
 :expression:`$dateAdd` report an error when an overflow is detected for
 ``amount`` values.
@@ -161,19 +158,13 @@ You can set the size of the :ref:`plan cache
 Change Streams
 --------------
 
-Optimization
-~~~~~~~~~~~~
-
 .. |change-streams| replace:: :ref:`change streams <changeStreams>`
 
 .. include:: /includes/change-streams-optimization.rst
 
 Indexes
 -------
 
-Convert a non-TTL single-field Index into a TTL Index
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
 Starting in MongoDB 5.1, you can use the :dbcommand:`collMod` database
 command to add the ``expireAfterSeconds`` option to an existing
 single-field non-TTL index.
@@ -245,8 +236,11 @@ determines whether the temporary documents required for :ref:`retryable
 <retryable-writes>` :dbcommand:`findAndModify` commands are stored in
 the *side* collection (``config.image_collection``).
 
+Sharded Clusters
+----------------
+
 ``mongod`` Sharded Cluster And Config Server Changes
-----------------------------------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Starting in MongoDB 5.1, when starting a :binary:`mongod` with the 
 :option:`--configsvr <mongod --configsvr>` option you must also