Update doc/api/next_api_changes/deprecations/30531-TH.rst

Co-authored-by: Elliott Sales de Andrade <[email protected]>

Author: timhoffm

doc/api/next_api_changes/deprecations/30531-TH.rst

@@ -1,6 +1,6 @@
 In-place modifications of colormaps
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Colormaps are planned to become immuatable in the long term.
+Colormaps are planned to become immutable in the long term.
 
 As a first step, in-place modifications of colormaps are now pending-deprecated.
 This affects the following methods of `.Colormap`: