DOC: update 1.15.1 relnotes

* Update the SciPy `1.15.1` release notes
after some backport activity.

Author: tylerjereddy

doc/source/release/1.15.1-notes.rst

@@ -5,19 +5,35 @@ SciPy 1.15.1 Release Notes
 .. contents::
 
 SciPy 1.15.1 is a bug-fix release with no new features
-compared to 1.15.0.
+compared to 1.15.0. Importantly, an issue with the
+import of `scipy.optimize` breaking other packages
+has been fixed.
 
 
 
 Authors
 =======
 * Name (commits)
+* Ralf Gommers (3)
+* Rohit Goswami (1)
+* Tyler Reddy (4)
+
+A total of 3 people contributed to this release.
+People with a "+" by their names contributed a patch for the first time.
+This list of names is automatically generated, and may not be fully complete.
 
 
 Issues closed for 1.15.1
 ------------------------
 
+* `#22257 <https://github.com/scipy/scipy/issues/22257>`__: BUG: Importing scipy.optimize break highspy
 
 
 Pull requests for 1.15.1
 ------------------------
+
+* `#22235 <https://github.com/scipy/scipy/pull/22235>`__: REL, MAINT: prep for 1.15.1
+* `#22245 <https://github.com/scipy/scipy/pull/22245>`__: MAINT: fix url for array-api-extra git submodule
+* `#22270 <https://github.com/scipy/scipy/pull/22270>`__: BLD: fix some issues with undeclared internal build dependencies
+* `#22272 <https://github.com/scipy/scipy/pull/22272>`__: TST: fix thread safety issue in interpolate.bsplines memmap test
+* `#22292 <https://github.com/scipy/scipy/pull/22292>`__: MAINT: Update highs subproject commit