[BOLT] Fix -jump-tables=basic in relocation mode.

Summary:
In a prev diff I added an option to update jump tables in-place (on by default)
and accidentally broke the default handling of jump tables in relocation
mode. The update should be happening semi-automatically, but because
we ignore relocations for jump tables it wasn't happening (derp).

Since we mostly use '-jump-tables=move' this hasn't been noticed for
some time.

This diff gets rid of IgnoredRelocations and removes relocations
from a relocation set when they are no longer needed. If relocations
are created later for jump tables they are no longer ignored.

(cherry picked from FBD4595159)