README: clarify nodejs is embedded by default in spec

[simonespa]

The "Dependencies" section should clarify that the "nodejs" RPM dependency is already embedded by default as both a "requirement" and a "build requirement" so it doesn't need to be specified.

See

speculate/templates/spec.hbs

Lines 15 to 19 in 37618f7

	Requires: nodejs{{#if nodeVersion}} {{{nodeVersion}}}{{/if}}
	{{#requires}}
	Requires: {{{.}}}
	{{/requires}}
	BuildRequires: nodejs{{#if nodeVersion}} {{{nodeVersion}}}{{/if}}