feat: allow removing deadline for running workspace (#16085)

Fixes https://github.com/coder/coder/issues/9775

When a workspace's TTL is removed, and the workspace is running, the
deadline is removed from the workspace.

This also modifies the frontend to not show a confirmation dialog when
the change is to remove autostop.

site/src/pages/WorkspaceSettingsPage/WorkspaceSchedulePage/WorkspaceSchedulePage.tsx

@@ -118,7 +118,10 @@ export const WorkspaceSchedulePage: FC = () => {
 
 						await submitScheduleMutation.mutateAsync(data);
 
-						if (data.autostopChanged) {
+						if (
+							data.autostopChanged &&
+							getAutostop(workspace).autostopEnabled
+						) {
 							setIsConfirmingApply(true);
 						}
 					}}