Release Notes: add back deprecation notices

I just noticed that those notices are not included in the -rc0 and -rc1
of v2.45.0, but let's add them back for the final v2.45.0 release
scheduled for this coming Monday, April 29th, 2024.

Please note that v2.45.0 will still support Windows 7/8 due to the move
to MSYS2 runtime v3.5.x being delayed (the MSYS2 project did not make
that switch yet, for similar reasons, and also because the quick
succession of the .0, .1, .2 and .3 releases raised doubts.).

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

ReleaseNotes.md

@@ -42,6 +42,10 @@ This package contains software from a number of other projects including Bash, z
 
 ## Changes since Git for Windows v2.44.0 (February 23rd 2024)
 
+Git for Windows for Windows v2.45 is the last version to support for Windows 7 and for Windows 8, see [MSYS2's corresponding deprecation announcement](https://www.msys2.org/docs/windows_support/) (Git for Windows relies on MSYS2 for components such as Bash and Perl).
+
+Please also note that the 32-bit variant of Git for Windows is deprecated; Its last official release [is planned for 2025](https://gitforwindows.org/32-bit.html).
+
 ### New Features
 
 * Comes with [PCRE2 v10.43](https://github.com/PCRE2Project/pcre2/releases/tag/pcre2-10.43).