In the standard text of hatarat nedarim, Artscroll has
וכל מיני נזירות שקבלתי עלי חוץ מנזירות שמשון
ואפילו נזירות שמשון
There are three types of nezirut (maseches Nazir 1,2): nezirut olam, nezirut Shimshon, and nezirut for a specified time period. (Nowadays the third one means "for a specified time period or until Mashiach comes, whichever is longer.)
If I had accepted any of these forms of nezirut (something I've never seriously considered and never plan to do, like 99.999% of people) and wanted to maintain it, I would explicitly exclude it myself in the hatara. I would do the same for any other vow I wanted to maintain. I assume that someone knowledgeable enough to accept nezirut Shimshon is also knowledgeable enough to change the text on the fly when necessary and not blindly follow the siddur.
Why does the standard text exclude or explicitly include nezirut Shimshon in particular but not the other forms? And where do the two versions come from?
(Actually, if it was up to me to exclude one of the three and I had to pick one, nezirut Shimshon would be my last choice. If you accepted a temporary nezirut, annulled it, and then brought the korbanot, you'd potentially be bringing chullin into the azarah, or at least an unnecessary chatat! Bad idea. Same if you accepted nezirut olam and then someone died near you. Apparently the standard text, like most of the siddur, is not Mashiach-proof, since it doesn't exclude any kind of korban vows.)