docs(how-to): remove unecessary decomposition

[openscript]

Description

getNodesByType is decomposed from the actions, but it's never used, so I removed it.

Documentation

Related Issues

[tyhopp]

Thanks! The final example does use getNodesByType in

gatsby/examples/creating-source-plugins/source-plugin/gatsby-node.js

Lines 149 to 150 in b5184cd

	getNodesByType(POST_NODE_TYPE).forEach(node => touchNode(node))
	getNodesByType(AUTHOR_NODE_TYPE).forEach(node => touchNode(node))

but I agree that it makes sense to remove it from the snippets in the doc since it's not used there.