qa/distros: remove a-supported-distro.yaml that pointed to centos 7.2

Signed-off-by: Casey Bodley <cbodley@redhat.com>

diff --git a/qa/distros/a-supported-distro.yaml b/qa/distros/a-supported-distro.yaml
deleted file mode 120000 (symlink)
index 33a40b6..0000000
--- a/qa/distros/a-supported-distro.yaml
+++ /dev/null
@@ -1 +0,0 @@
-all/centos_7.2.yaml
\ No newline at end of file