Update yarn.lock on greenkeeper PR's (#7885)

* update yarn.lock on greenkeeper prs
* chore: yarn.lock

.travis.yml

@@ -45,6 +45,19 @@ install:
   - if [ "$DB" == "sqlite3" ]; then yarn add --force sqlite3; fi # fix sqlite caching issues
 
 after_success:
+  - |
+      if [ "$DB" != "sqlite3" ] || [ "$TRAVIS_NODE_VERSION" != "4" ] || [[ "$TRAVIS_PULL_REQUEST_BRANCH" != *"greenkeeper"* ]]; then
+        exit 0
+      fi
+      git clone -b "$TRAVIS_PULL_REQUEST_BRANCH" "https://"$PUSH_TOKEN"@github.com/"$TRAVIS_REPO_SLUG".git" repo && cd repo
+      git log --name-status HEAD^..HEAD | grep "update" || exit 0
+      yarn
+      git config --global user.email "github@ghost.org"
+      git config --global user.name "TryGhost-Travis"
+      git config --global push.default simple
+      git add yarn.lock
+      git commit -m "chore: yarn.lock"
+      git push
   - |
       if [ "$TRAVIS_PULL_REQUEST" = "false" ]; then
         if [[ "$DB" = "sqlite3" && "$TRAVIS_NODE_VERSION" = "4" ]]; then

yarn.lock

@@ -3346,9 +3346,9 @@ klaw@^1.0.0:
   optionalDependencies:
     graceful-fs "^4.1.9"
 
-knex-migrator@1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/knex-migrator/-/knex-migrator-1.0.0.tgz#a9e8de60ed5807e193c3300f733fcdec463dc63e"
+knex-migrator@1.1.1:
+  version "1.1.1"
+  resolved "https://registry.yarnpkg.com/knex-migrator/-/knex-migrator-1.1.1.tgz#b44b5d3b721bd4f6efd090b1d64aa0fae6fbbe77"
   dependencies:
     bluebird "3.4.6"
     coloured-log "0.9.7"