DOC: Fix "``s" pattern in changelog

Author: effigies

Changelog

@@ -79,7 +79,7 @@ Enhancements
 
 Bug fixes
 ---------
-* Sliced ``Tractogram``s no longer ``apply_affine`` to the original
+* Sliced ``Tractogram``\s no longer ``apply_affine`` to the original
   ``Tractogram``'s streamlines. (pr/811) (MC, reviewed by Serge Koudoro,
   Philippe Poulin, CM, MB)
 * Change strings with invalid escapes to raw strings (pr/827) (EL, reviewed
@@ -98,7 +98,7 @@ Maintenance
 API changes and deprecations
 ----------------------------
 * Fully remove deprecated ``checkwarns`` and ``minc`` modules. (pr/852) (CM)
-* The ``keep_file_open`` argument to file load operations and ``ArrayProxy``s
+* The ``keep_file_open`` argument to file load operations and ``ArrayProxy``\s
   no longer acccepts the value ``"auto"``, raising a ``ValueError``. (pr/852)
   (CM)
 * Deprecate ``ArraySequence.data`` in favor of ``ArraySequence.get_data()``,
@@ -420,7 +420,7 @@ New features
 * Support for MRtrix TCK streamlines file format (pr/486) (MC, reviewed by
   MB, Arnaud Bore, J-Donald Tournier, Jean-Christophe Houde)
 * Added ``get_fdata()`` as default method to retrieve scaled floating point
-  data from ``DataobjImage``s (pr/551) (MB, reviewed by CM, SG)
+  data from ``DataobjImage``\s (pr/551) (MB, reviewed by CM, SG)
 
 Enhancements
 ------------