PHILADELPHIA — President Joe Biden’s decision to pardon thousands of Americans convicted of “simple possession” of marijuana in federal court elicited celebration from Democratic Senate candidate John Fetterman, who has long advocated for legalizing the drug, and silence from his Republican challenger, Mehmet Oz. Fetterman called the announcement a “a massive step toward justice,” and claimed some credit. He’d pressed Biden on the issue when they both marched in the Pittsburgh Labor Day parade. “When I heard President Biden would be in Pittsburgh a month ago, I knew that if I had a chance to s…