docs(changelog): add the #1718 fragment

Co-Authored-By: Claude Fable 5.2 <[email protected]>

changelog.d/1718-nvg-flir-blur.md

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+- NVG and FLIR redraw 15 times a second instead of 60 when nothing else is
+  moving, and their bloom reads a fifth to a half as many texels per pixel for
+  the same picture. Their grain now changes 15 times a second (mazy1998,
+  #1718).