^Huh? What's pronunciation got to do with word order? And how is Shatner's pronunciation of "to boldly go" in any way unusual?
It's not. But lines can be tailored to suit the actors who are saying them. Kirk's preamble was by various accounts one of the last things settled on by the production team in TOS, and a few versions were tested. Shatner is the king of speaking iambic pentameter, and that particular arrangement of the phrase suits both him and
his character, Captain James Tiberius Kirk. There's no shame in that whatsoever.