[FAB-13282] Clarify version of node.js
[FAB-13282] Clarify version of node.js

The current wording in the prerequisite document is unclear with regards to
which version of node.js is required.

Change-Id: I2529ad712d7f4f3a371967fe37e1e5198d2a1614
Signed-off-by: Alessandro Sorniotti <f32b00f17cd31d4086a37e20e6815a9429f62787@sopit.net>

jimthematrix/fabric,stemlending/fabric,muralisrini/fabric,manish-sethi/fabric,stemlending/fabric,hyperledger/fabric,binhn/fabric,manish-sethi/fabric-sidedb,stemlending/fabric,manish-sethi/fabric-sidedb,binhn/fabric,manish-sethi/fabric,muralisrini/fabric,jimthematrix/fabric,hyperledger/fabric,muralisrini/fabric,manish-sethi/fabric-sidedb,binhn/fabric,manish-sethi/fabric-sidedb,manish-sethi/fabric-sidedb,manish-sethi/fabric-sidedb,manish-sethi/fabric-sidedb,stemlending/fabric