Update links to GPO and the Gray book on the statute page

[dorothyyeager]

User Story As someone who needs to comply with or research federal campaign finance law, it's helpful to have the latest version of the U.S. Code.

Background GPO is making many website changes and is moving its federal database to https://www.govinfo.gov/. Our links on https://www.fec.gov/data/legal/statutes/ to Titles 52 and 26, USC point to the old database and the 2015 edition. We should find the latest editions on the new database at https://www.govinfo.gov/app/collection/uscode (right now it is 2016 for Title 52 and 2017 for Title 26) and update the page.

This work requires a simple update to the hard-coded part of the page (so simple the content team did it last time! - see #2181 for example to follow).

To do

• Find the latest versions of Title 52 and 26 from govinfo.gov
• Update the hard-coded version to update the links to the latest versions (will need a PR).
• Upload the updated PDF for 2019 to replace the current file. (It's ready by this sprint.)

[dorothyyeager]

2017 version of Title 52 is up on govinfo.gov - https://www.govinfo.gov/app/details/USCODE-2017-title52/USCODE-2017-title52-subtitleIII-chap301

[dorothyyeager]

The 2019 edition of the gray book has been uploaded to https://www.fec.gov/resources/cms-content/documents/feca.pdf

Latest files from govinfo.gov for when we tackle the hard-coding:
Title 52: https://www.govinfo.gov/app/details/USCODE-2017-title52/USCODE-2017-title52-subtitleIII-chap301
Link to: https://www.govinfo.gov/content/pkg/USCODE-2017-title52/pdf/USCODE-2017-title52-subtitleIII-chap301.pdf

Title 26: https://www.govinfo.gov/app/details/USCODE-2017-title26/USCODE-2017-title26-subtitleH - link to: https://www.govinfo.gov/content/pkg/USCODE-2017-title26/pdf/USCODE-2017-title26-subtitleH.pdf

[dorothyyeager]

PR has been approved and merged, so this is ready to close.