Update research-guidelines.md (#3819)

* Update research-guidelines.md

Removed broken links. I also ran the W3C link checker, which found a lot of other issues: 
https://validator.w3.org/checklink?uri=https%3A%2F%2Fhandbook.tts.gsa.gov%2F18f%2Fhow-18f-works%2Fresearch-guidelines%2F&hide_type=all&depth=&check=Check

* Update pages/18f/how-18f-works/research-guidelines.md

* Update pages/18f/how-18f-works/research-guidelines.md

---------

Co-authored-by: John Skiles Skinner <john.skinner@gsa.gov>

pages/18f/how-18f-works/research-guidelines.md

@@ -287,10 +287,7 @@ post it in Slack.
 Carefully restricting access to personally identifiable information is a matter
 not just of people's right to respect but of their right to
 [privacy](https://methods.18f.gov/privacy/). For more information, please see
-the
-[Design research privacy impact assessment (PIA)](https://www.gsa.gov/cdnstatic/20200401_-_Design_Research_PIA_for%20posting.pdf),
-or
-[this 30-minute overview of privacy as it relates to research](https://gsa-tts.slack.com/files/U9KLLKS4W/FCSFWBZD3/researchguildprivacytalk091218.mp4)
+[this 30-minute overview of privacy as it relates to research](https://gsa-tts.slack.com/archives/C03JK2KH8/p1536779475000100)
 narrated by the GSA Privacy Office.
 
 **Bottom line: If you have questions about sharing information, just ask.** See
@@ -304,5 +301,4 @@ Portfolio]({% page "/office-of-solutions/tech-portfolio/#questions" %}).
 ## Join the research guild!
 
 Learn more about the research guild in our [README.](https://docs.google.com/document/d/1kc73HuxXWxr4RIKG0aeHSW3VFK5SRD597vZNfX4_huM/edit#heading=h.wdpwcv6e5j47)
-
-[Learn more about guilds at TTS here.]({% page "/training-and-development/working-groups-and-guilds-101/#current-guilds" %})
+[Learn more about guilds at TTS here.]({% page "/training-and-development/working-groups-and-guilds-101/#current-guilds" %})