By Dawn Chmielewski (Reuters) -Spotify Technology SA on Tuesday said third-quarter profit margins were squeezed by slow advertising growth, fanning concerns about the weak global economy’s effect on digital advertising. Spotify shares slid 4% in after-hours trading, stung by sector-wide weakness after Google parent Alphabet Inc missed market estimates for quarterly revenue as advertisers cut spending. Spotify, whose stock has fallen 58.5% this year, said third-quarter margins were less than it had expected, blaming “some softness in advertising,” currency fluctuations and retroactive royalty p…