Update requests library to resolve security vulnerability in urllib3

[jason-upchurch]

Summary (required)

• Resolves [Snyk: High] requirement - HTTP Header Injection (due 11/06/2020) #4106

Impacted areas of the application

List general components of the application that this PR will affect:

• requests library

How to test

Verify vulnerability

1. checkout develop branch
2. from fec-cms project root, ensure develop branch requirements.txt are installed
3. snyk test --file=requirements.txt (you should see the vulnerability listed, if not, let's discuss)

Verify vulnerability resolution

1. checkout this PR
2. from fec-cms project root, ensure PR branch requirements.txt are installed
3. snyk test --file=requirements.txt (the vulnerability should not longer be listed)

Verify the vulnerability resolution did not break anything

1. pytest
2. I did a manual deploy of this branch to dev space and it build successfully. I verified a few datatable returns. Please feel free to deploy and test further.

Additional considerations

1. While testing, I saw the build give some warnings that also exist in develop (note the 404s):

 HeadlessChrome 78.0.3882 (Linux 0.0.0): Executed 382 of 434 (skipped 1) SUCCESS (0 secs / 0.847 secs)
HeadlessChrome 78.0.3882 (Linux 0.0.0): Executed 383 of 434 (skipped 1) SUCCESS (0 secs / 0.849 secs)
HeadlessChrome 78.0.3882 (Linux 0.0.0): Executed 384 of 434 (skipped 1) SUCCESS (0 secs / 0.849 secs)
16 10 2020 10:52:30.492:WARN [web-server]: 404: /v1/candidates/totals/?api_key=12345&sort=-receipts&per_page=10&sort_hide_null=true&election_year=2016&election_full=true&office=P&is_active_candidate=true&page=1
16 10 2020 10:52:30.493:WARN [web-server]: 404: /v1/candidates/totals/?api_key=12345&sort=-receipts&per_page=10&sort_hide_null=true&election_year=2016&election_full=true&office=P&is_active_candidate=true&page=1

2. I opened an issue to investigate these (Investigate test warnings #4127)
3. the vulnerability resolution in urllib3 requires upgrade to parent package requests

[codecov-io]

Codecov Report

Merging #4126 into develop will increase coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #4126      +/-   ##
===========================================
+ Coverage    75.47%   75.48%   +0.01%     
===========================================
  Files          121      121              
  Lines         7417     7417              
  Branches       596      596              
===========================================
+ Hits          5598     5599       +1     
+ Misses        1819     1818       -1     

Impacted Files	Coverage Δ
fec/fec/static/js/modules/calendar.js	92.64% <0.00%> (+0.73%)	⬆️

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[patphongs]

Looks good, we use requests and urllib inside api_caller.py, so I tested to make sure that still loads