Local History: Set Max Size Per Project (MB)…
history.setMaxTotalMb Limit the size of one project's Local History, counted as uncompressed text. Each file's newest revision, labelled revisions and copies taken before a delete are kept even over the limit.
How to run it
Open the command palette (M-x in the Emacs keymap) and search for Local History: Set Max Size Per Project (MB)…, then press Enter. It has no default keybinding, but you can bind one in Settings → Keymaps.