Fix "info registers" regexes in gdb.base/jit-reader.exp

Commit

  e813d34a ("Align natural-format register values to the same column")

changed the output of "info registers" (tabs to spaces), but didn't
update gdb.base/jit-reader.exp.  Update the regexes to expect spaces
instead.

gdb/testsuite/ChangeLog:

	* gdb.base/jit-reader.exp (jit_reader_test): Expect spaces in
	"info registers" output.