builtin/blame.c: constants into bit shift format

builtin/blame.c: constants into bit shift format

We are looking at bitfield constants, and elsewhere in the Git source
code, such cases are handled via bit shift operators rather than octal
numbers, which also makes it easier to spot holes in the range
(if, say, 1<<5 was missing, it is easier to spot it between 1<<4
and 1<<6 than it is to spot a missing 040 between a 020 and a 0100).

Signed-off-by: Hariom Verma <redacted>
Signed-off-by: Junio C Hamano <redacted>