Reduce depth of formatted statements

Only print the first level. For arrays/maps/objects/sets this means the
indexes/keys are printed. Presumably since we do print all statements
this provides enough context.

lib/enhance-assert.js

@@ -37,7 +37,7 @@ const formatter = context => {
 	return args
 		.map(arg => {
 			const range = getNode(ast, arg.espath).range;
-			return [computeStatement(tokens, range), formatValue(arg.value)];
+			return [computeStatement(tokens, range), formatValue(arg.value, {maxDepth: 1})];
 		})
 		.reverse();
 };