Fix typo

scripts/create_venv.sh

-#!/bin/bin/env bash
+#!/usr/bin/env bash
 if [ ! -d "venv" ]; then
     echo "Creating a fresh virtualenv..."
     pip install -U pip setuptools wheel

scripts/get_pdfs.sh

-#!/bin/bin/env bash
+#!/usr/bin/env bash
 if [ ! -d "pdfs" ]; then
     echo "Retrieving PDFs..."
     mkdir pdfs