Update python binary name for py2 in deb_old_option_tester CI template

.gitlab-opttest-ci.yml

@@ -126,7 +126,7 @@ freebsd-options-tester:
   script:
     - apt-get update
     - apt-get install -y netbase bison gcc libssl-dev libcap-dev pps-tools python2-dev python2-minimal libseccomp-dev bash pkg-config python3-dev python3-minimal
-    - PYTHON=python bash tests/option-tester.sh
+    - PYTHON=python2 bash tests/option-tester.sh
     - PYTHON=python3 bash tests/option-tester.sh
   tags:
     - gitlab-org