Do not print statistics when using in stdout mode

When using the `stdout` output mode (e.g. using `svgo -` within a
pipeline), the time and optimization statistics shouldn't be printed in
the output stream.

lib/svgo/coa.js

@@ -399,8 +399,8 @@ function processSVGData(config, info, data, output, input) {
             processingTime = Date.now() - startTime;
 
         return writeOutput(input, output, result.data).then(function() {
-            if (!config.quiet) {
-                if (input && output != '-') {
+            if (!config.quiet && output != '-') {
+                if (input) {
                     console.log(`\n${PATH.basename(input)}:`);
                 }
                 printTimeInfo(processingTime);