removing mul_assoc lemma
removing mul_assoc lemma

aa755/FStar,YaccConstructor/FStar,msprotz/FStar,msprotz/FStar,MallabaevAzamat/FStar,aa755/FStar,aa755/FStar,MallabaevAzamat/FStar,A-Manning/FStar,A-Manning/FStar,msprotz/FStar,MallabaevAzamat/FStar,hoheinzollern/FStar,hoheinzollern/FStar,hoheinzollern/FStar,aa755/FStar,FStarLang/FStar,YaccConstructor/FStar,MallabaevAzamat/FStar,YaccConstructor/FStar,msprotz/FStar,YaccConstructor/FStar,A-Manning/FStar,FStarLang/FStar,FStarLang/FStar,hoheinzollern/FStar