DRIVERS-2789 Convert GridFS Spec to Markdown

Remove old readme

Update source/gridfs/gridfs-spec.md

Co-authored-by: Jeremy Mikola <[email protected]>

address review

Author: blink1073

source/client-side-operations-timeout/client-side-operations-timeout.md

@@ -92,7 +92,7 @@ The `timeoutMS` option applies to all operations defined in the following specif
 - [Client Side Encryption](../client-side-encryption/client-side-encryption.md)
 - [Enumerating Collections](../enumerate-collections.rst)
 - [Enumerating Databases](../enumerate-databases.rst)
-- [GridFS](../gridfs/gridfs-spec.rst)
+- [GridFS](../gridfs/gridfs-spec.md)
 - [Index Management](../index-management/index-management.rst)
 - [Transactions](../transactions/transactions.md)
 - [Convenient API for Transactions](../transactions-convenient-api/transactions-convenient-api.rst)

source/client-side-operations-timeout/client-side-operations-timeout.rst

@@ -137,7 +137,7 @@ specifications:
 - `Client Side Encryption <../client-side-encryption/client-side-encryption.md>`__
 - `Enumerating Collections <../enumerate-collections.rst>`__
 - `Enumerating Databases <../enumerate-databases.rst>`__
-- `GridFS <../gridfs/gridfs-spec.rst>`__
+- `GridFS <../gridfs/gridfs-spec.md>`__
 - `Index Management <../index-management/index-management.rst>`__
 - `Transactions <../transactions/transactions.rst>`__
 - `Convenient API for Transactions <../transactions-convenient-api/transactions-convenient-api.rst>`__