perf annotate browser: Don't change the asm line color when toggling source

Gets confusing. Remains to be chosen an appropriate different color for
source code.

This effectively reverts 58e817d9

 ("perf annotate: Print asm code as
blue when source code is displayed")

Requested-by: Peter Zijlstra <peterz@infradead.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-qy9iq32nj3uqe5dbiuq9e3j9@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>