It's a technical term, but not the technical term you are thinking of.
In this case, "regular" means composed of few rules with with few corner cases.
The term for a grammar that describes a regular language is usually left-linear or right-linear, "regular grammar" in this sense is rather uncommon. A compact notation for describing regular languages are regular expressions.
Go's grammar is not in CH-3, i.e. not regular in that sense of the word, but it has a lot less corner cases than, say, Java, C#, C++ or C, so it is a lot more regular (in the other sense) than those.