main/postgresql-common: add secfixes comment for CVE-2019-3466

This CVE never affected alpine. Add secixes data to silence security
scanners.

main/postgresql-common/APKBUILD

@@ -17,6 +17,10 @@ source="pg_versions
 builddir="$srcdir"
 options="!check"  # no tests
 
+# secfixes:
+#   0:
+#     - CVE-2019-3466
+
 package() {
 	mkdir -p "$pkgdir"