As long as that is the version of mIRC you know you're using, yes, ignore it. The system restore is just there because there's a "copy" that is being detected in there.
I haven't had McAfee throw that at me recently, but I probably already have mIRC set as safe or else I disabled checking for PUPs. Anyhow, it is only unsafe if you use it unsafely. Obviously, you can get viruses/trojans/etc. by using mIRC if you're not careful (such as downloading things from untrusted sources, typing things that people tell you to type without knowing what it does, running unknown and untrusted scripts, etc). But if you don't do that sort of thing, it's as safe as any other internet application (and safer than some).
Basically, a PUP isn't a danger as long as you trust the program.
