RexEx inconsistencies (#7022)

* re-add expression

* removing unexpected file changes

* update docs to agree on the supported regex options

* remove duplicate info and point to more detailed page

* wordsmithing; remote info box

Author: MongoCaleb

source/reference/mongodb-extended-json.txt

@@ -585,15 +585,9 @@ Where the values are as follows:
 
 - ``"<options>"``
 
-  - A string that specifies BSON regular expression options ('g', 'i',
-    'm' and 's') or an empty string ``""``.
-          
-  - Options other than ('g', 'i', 'm' and 's') will be dropped when
-    converting to this representation.
-
-  .. important::
-
-     The options MUST be in alphabetical order.
+  - A string that specifies BSON regular expression options. You must specify 
+    the options in alphabetical order. For information on the supported options, 
+    see :query:`$options`.
 
 .. bsontype:: Timestamp
 

source/reference/operator/query/regex.txt

@@ -87,16 +87,14 @@ expression.
 
 .. list-table::
    :header-rows: 1
-   :widths: 10 60 30
+   :widths: 20 80
 
    * - Option
      - Description
-     - Syntax Restrictions
 
    * - ``i``
      - Case insensitivity to match upper and lower cases. For an
        example, see :ref:`regex-case-insensitive`.
-     -
 
    * - ``m``
 
@@ -110,8 +108,6 @@ expression.
        no newline characters (e.g. ``\n``), the ``m`` option has no
        effect.
 
-     -
-
    * - ``x``
 
      - "Extended" capability to ignore all white space characters in
@@ -128,20 +124,21 @@ expression.
        The ``x`` option does not affect the handling of the VT
        character (i.e. code 11).
 
-     - Requires ``$regex`` with ``$options`` syntax
-
    * - ``s``
 
      - Allows the dot character (i.e. ``.``) to match all
        characters *including* newline characters. For an example,
        see :ref:`regex-dot-new-line`.
 
-     - Requires ``$regex`` with ``$options`` syntax
+   * - ``u``
+
+     -  Supports Unicode. This flag is accepted, but is redundant. UTF is set by 
+        default in the ``$regex`` operator, making the ``u`` option 
+        unnecessary. 
 
 .. note:: 
 
-   The ``$regex`` operator does not support the global search
-   modifier ``g``.
+   The ``$regex`` operator *does not* support the global search modifier ``g``.
 
 Behavior
 --------