[v2] tutorial part one: fix path to about.js page (#7323)
[v2] tutorial part one: fix path to about.js page (#7323)

Point no 6 under the header What are “props”? wrongly pointed to header component
Changed it to point to src/pages/about.js
mingaldrichgan/gatsby,0x80/gatsby,0x80/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,ChristopherBiscardi/gatsby,ChristopherBiscardi/gatsby,gatsbyjs/gatsby,ChristopherBiscardi/gatsby,gatsbyjs/gatsby,0x80/gatsby,mingaldrichgan/gatsby,ChristopherBiscardi/gatsby,mingaldrichgan/gatsby