main/npm: replace dependency nodejs with cmd:node

Command 'node' is provided by packages nodejs (highest priority)
and nodejs-current.

main/npm/APKBUILD

@@ -7,7 +7,7 @@ pkgdesc="The package manager for JavaScript"
 url="https://npm.community"
 arch="noarch !mips64 !mips64el"  # limited by nodejs
 license="Artistic-2.0"
-depends="nodejs"
+depends="cmd:node"
 makedepends="bash"
 replaces="nodejs-doc"  # for backward compatibility
 subpackages="$pkgname-doc $pkgname-bash-completions:bashcomp"