SAN FRANCISCO – Paul Blackburn may have grown up a Giants fan, but the Giants were no fan of the A’s right-hander Wednesday night. The ex-Heritage High of Oakley standout made himself at home at the same stadium where he rooted for his favorite team, blanking the Giants over five innings to get the win in the A’s 1-0 victory. Oakland snapped San Francisco’s five-game winning streak to earn a split in the two-game Bay Bridge Series at Oracle Park in front of 32,014. Blackburn, who’s proven to be a revelation early in his sixth season, lowered his earned run average to 1.35 after shutting the Gi…