Portable trap conditions in run-test.sh.

Posix says:
    The condition can be EXIT, 0 (equivalent to EXIT), or a signal
    specified using a symbolic name, without the SIG prefix, as listed
    in the tables of signal names in the <signal.h> header defined in
    the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 13,
    Headers; for example, HUP, INT, QUIT, TERM. Implementations may
    permit names with the SIG prefix or ignore case in signal names as
    an extension.

Remove 'SIG' from trap conditions in run-test.sh for portability.
10 jobs for run_test_trap_no_SIG in 8 minutes and 13 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Build
passed #6105849
gst-macos-10.15
meson macos

00:03:10

passed #6105846
meson-mingw-w64-build

00:04:52

manual #6105850
docker windows 1809 allowed to fail manual
meson msys2
passed #6105844
meson-shared-build

00:05:09

passed #6105845
meson-static-build

00:05:38

passed #6105847
docker windows 1809
meson vs2017 amd64

00:01:25

passed #6105848
docker windows 1809
meson vs2017 x86

00:01:26

passed #6105843
mingw-build

00:05:50

passed #6105841
shared-build

00:08:13

passed #6105842
static-build

00:06:54