Fix pulling licenses

[damccorm]

Right now, https://ci-beam.apache.org/job/beam_PreCommit_Portable_Python_Cron/ and https://ci-beam.apache.org/job/beam_PreCommit_PythonDocker_Cron/ are permared because of the following error:

ERROR:root:Error occurred when pull license for flatbuffers from {'license': 'https://raw.githubusercontent.com/google/flatbuffers/master/LICENSE.txt'}.
05:31:13 Traceback (most recent call last):
05:31:13   File "/tmp/license_scripts/pull_licenses_py.py", line 98, in pull_from_url
05:31:13     headers={'User-Agent': 'Apache Beam'}))
05:31:13   File "/usr/local/lib/python3.7/urllib/request.py", line 222, in urlopen
05:31:13     return opener.open(url, data, timeout)
05:31:13   File "/usr/local/lib/python3.7/urllib/request.py", line 531, in open
05:31:13     response = meth(req, response)
05:31:13   File "/usr/local/lib/python3.7/urllib/request.py", line 641, in http_response
05:31:13     'http', request, response, code, msg, hdrs)
05:31:13   File "/usr/local/lib/python3.7/urllib/request.py", line 569, in error
05:31:13     return self._call_chain(*args)
05:31:13   File "/usr/local/lib/python3.7/urllib/request.py", line 503, in _call_chain
05:31:13     result = func(*args)
05:31:13   File "/usr/local/lib/python3.7/urllib/request.py", line 649, in http_error_default
05:31:13     raise HTTPError(req.full_url, code, msg, hdrs, fp)
05:31:13 urllib.error.HTTPError: HTTP Error 404: Not Found

this is because of google/flatbuffers@7fb785f

This fixes with the new path

---

Thank you for your contribution! Follow this checklist to help us incorporate your contribution quickly and easily:

• Mention the appropriate issue in your description (for example: addresses #123), if applicable. This will automatically add a link to the pull request in the issue. If you would like the issue to automatically close on merging the pull request, comment fixes #<ISSUE NUMBER> instead.
• Update CHANGES.md with noteworthy changes.
• If this contribution is large, please file an Apache Individual Contributor License Agreement.

See the Contributor Guide for more tips on how to make review process smoother.

To check the build health, please visit https://github.com/apache/beam/blob/master/.test-infra/BUILD_STATUS.md

GitHub Actions Tests Status (on master branch)

See CI.md for more information about GitHub Actions CI.

[damccorm]

https://ci-beam.apache.org/job/beam_PostCommit_XVR_Samza_PR/54/console hit this as well

[damccorm]

R: @johnjcasey

[github-actions]

Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control

[johnjcasey]

LGTM

[codecov]

Codecov Report

Merging #25234 (200106c) into master (634b045) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #25234      +/-   ##
==========================================
- Coverage   72.97%   72.97%   -0.01%     
==========================================
  Files         743      743              
  Lines       99037    99037              
==========================================
- Hits        72271    72268       -3     
- Misses      25400    25403       +3     
  Partials     1366     1366              

Flag	Coverage Δ
python	82.50% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...eam/runners/portability/fn_api_runner/execution.py	92.49% <0.00%> (-0.64%)	⬇️
...on/apache_beam/runners/dataflow/dataflow_runner.py	81.88% <0.00%> (+0.14%)	⬆️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more