With bug #87648 fixed at https://cgit.freedesktop.org/libreoffice/core/commit/?id=1098fba99acb8c8cc7e87c55ece12ef175593147 We need to update the helpcontent in places it refers the Spelling and Grammar menu item / window: https://opengrok.libreoffice.org/search?project=help&q=%22Spelling+and+Grammar%22&defs=&refs=&path=&hist=&type=
As said in the patch, the change can be applied to the menu and references to the menu in help pages. But on other help pages, which describe the functionality, spell check comes often together with grammar check, sl some help page stay as is.
Olivier Hallot committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/help/commit/?id=b5d455e09862a98eba8209445f859de29c1e449e tdf#112015 Spelling and Grammar -> Spelling