make logs consistent

src/main/announcement.js

@@ -32,7 +32,7 @@ function init () {
 
 function onResponse (err, res, data) {
   if (err) return log(`Failed to retrieve announcement: ${err.message}`)
-  if (res.statusCode !== 200) return log('No announcement exists')
+  if (res.statusCode !== 200) return log('No announcement available')
 
   try {
     data = JSON.parse(data.toString())

src/main/updater.js

@@ -63,7 +63,7 @@ function initDarwinWin32 () {
 
   electron.autoUpdater.on(
     'update-not-available',
-    () => log('Update not available')
+    () => log('No update available')
   )
 
   electron.autoUpdater.on(