Fix Source.constructSource to use versionSpec instead of parsedVersionSpec

[xhalo32]

Previously, parsedVersionSpec was passed to NPMRegistrySource.prototype.fetch which stripped the alias if the versionSpec also contained a semver range, like npm:@codingame/monaco-vscode-api@ >= 1.69.0 < 1.70.0.

This change removes the semver parsing from Source.constructSource as it is the rensponsibility of NPMRegistrySource.prototype.fetch.

Fixes #331