chore(deps): update dependency ava to ^0.25.0 (#37)

Author: renovate[bot]

texttospeech/package-lock.json

@@ -18,7 +18,7 @@
   },
   "devDependencies": {
     "@google-cloud/nodejs-repo-tools": "^2.3.0",
-    "ava": "^0.23.0"
+    "ava": "^0.25.0"
   },
   "optionalDependencies": {
     "canvas": "^1.6.5"