Delete unused devDependencies

[fhinkel]

proxiquire is a good candidate.

appengine/analytics/package.json
appengine/building-an-app/build/package.json
appengine/building-an-app/update/package.json
appengine/cloudsql/package.json
appengine/cloudsql_postgresql/package.json
appengine/datastore/package.json
appengine/endpoints/package.json
appengine/headless-chrome/package.json
appengine/hello-world/flexible/package.json
appengine/hello-world/standard/package.json
appengine/loopback/package.json
appengine/mailjet/package.json
appengine/memcached/package.json
appengine/metadata/flexible/package.json
appengine/metadata/standard/package.json
appengine/mongodb/package.json
appengine/parse-server/package.json
appengine/pubsub/package.json
appengine/redis/package.json
appengine/sendgrid/package.json
appengine/static-files/package.json
appengine/storage/flexible/package.json
appengine/storage/standard/package.json
appengine/twilio/package.json
appengine/typescript/package.json
appengine/uglifyjs/package.json
auth/package.json
containerengine/hello-world/package.json
debugger/package.json
endpoints/getting-started-grpc/package.json
endpoints/getting-started/package.json
functions/background/package.json
functions/billing/package.json
functions/composer-storage-trigger/package.json
functions/concepts/package.json
functions/datastore/package.json
functions/env_vars/package.json
functions/errorreporting/package.json
functions/firebase/package.json
functions/gcs/package.json
functions/headless-chrome/package.json
functions/helloworld/package.json
functions/http/package.json
functions/imagemagick/package.json
functions/log/package.json
functions/node8/package.json
functions/ocr/app/package.json
functions/pubsub/package.json
functions/scheduleinstance/package.json
functions/sendgrid/package.json
functions/slack/package.json
functions/spanner/package.json
functions/speech-to-speech/package.json
functions/sql/package.json
functions/tips/package.json
functions/uuid/package.json
healthcare/datasets/package.json
healthcare/dicom/package.json
healthcare/fhir/package.json
healthcare/hl7v2/package.json
iot/beta-features/commands/receive/package.json
iot/beta-features/commands/send/package.json
iot/http_example/package.json
iot/manager/package.json
iot/mqtt_example/package.json
iot/scripts/package.json
jobs/cjd_sample/package.json
kms/package.json
language/slackbot/package.json
memorystore/redis/package.json
storage-transfer/package.json
trace/package.json