src/util: change TriBool logic to use a bool template parameter

src/p_lx_elf.cpp

@@ -2974,8 +2974,7 @@ tribool PackLinuxElf64::canUnpack() // bool, except -1: format known, but not pa
     return false;
 }
 
-tribool
-PackLinuxElf64::canPack()
+tribool PackLinuxElf64::canPack()
 {
     union {
         unsigned char buf[MAX_ELF_HDR_64];