Go to File -> Open .osu in Notepad
Go to the "Events" section (Just look for the line that writes "[Events]".), below the "//Break Periods" line, delete the one you want to, with the syntax:
2,[Start of the break],[End of the break]
Note: The editor will add breaks for you if it's long enough so recommend
only delete them when they're short enough that the editor don't automatically add anything inbetween.