Use shfmt for bash instead of sh.

Similar reason as previous commit;
3eeff04c9b, use `shellcheck` for `bash`
instead of `sh`.
`sh` files get their filetype set to `bash`, for treesitter to function
properly.

.config/nvim/lua/plugin/conform.lua

@@ -10,7 +10,7 @@ require('conform').setup({
 		typescript = { 'clang-format', lsp_format = "first" },
 		css        = { 'clang-format' },
 		rust       = { 'rustfmt' },
-		sh         = { 'shfmt' },
+		bash       = { 'shfmt' },
 		python     = { 'isort' },
 		-- json   = { 'jq' },
 		-- yaml       = { 'yq' },