fix(userspace/falco): add missing pragma once

Signed-off-by: Jason Dellaluce <jasondellaluce@gmail.com>

userspace/falco/versions_info.h

@@ -14,6 +14,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+#pragma once
+
 #include <memory>
 #include <string>
 #include <unordered_map>