send-pull-request: unset $TO and $CC from environment

Darren Hart and I discovered that when $CC is set (which
our meta-toolchain environment script sets up), the value
leaks into the use of this script. Unsetting $TO as well
just to be thorough.

Signed-off-by: Scott Garman <scott.a.garman@intel.com>

scripts/send-pull-request

@@ -6,6 +6,10 @@ if [ -z "$PULL_MTA" ]; then
     PULL_MTA="sendmail"
 fi
 
+# Prevent environment leakage to these vars.
+unset TO
+unset CC
+
 usage()
 {
 cat <<EOM