Replace node 11.4 with 11.3 because it is the most recent version in the last buildpack release
Replace node 11.4 with 11.3 because it is the most recent version in the last buildpack release

Co-authored-by: Zander Mackie <320db42c0fea4ffbf0ae28d5036748df300aa745@pivotal.io>

cloudfoundry/nodejs-buildpack,cloudfoundry/nodejs-buildpack,cloudfoundry/nodejs-buildpack,cloudfoundry/nodejs-buildpack