Update Doc/whatsnew/3.15.rst

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Author: warsaw

Doc/whatsnew/3.15.rst

@@ -91,7 +91,7 @@ Summary -- Release highlights
 * :ref:`Improved error messages <whatsnew315-improved-error-messages>`
 * :ref:`The official Windows 64-bit binaries now use the tail-calling interpreter
   <whatsnew315-windows-tail-calling-interpreter>`
-* :pep:`829`: :ref:`Package Startup Configuration Files <whatsnew315-startup-files>`
+* :pep:`829`: :ref:`Package startup configuration files <whatsnew315-startup-files>`
 
 New features
 ============