Change update_version.sh to reflect the renaming of dropbox/dropbox.py

[yuxiang-he]

Checklist

General Contributing

• Have you read the Code of Conduct and signed the CLA?

Is This a Code Change?

• Non-code related change (markdown/git settings etc)
• SDK Code Change
• Example/Test Code Change

Validation

• Does tox pass?
• Do the tests pass?

[codecov]

Codecov Report

Merging #294 (d558479) into main (0f1ad58) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #294   +/-   ##
=======================================
  Coverage   63.58%   63.58%           
=======================================
  Files          30       30           
  Lines       48223    48223           
  Branches     3537     3537           
=======================================
  Hits        30662    30662           
  Misses      17533    17533           
  Partials       28       28           

Flag	Coverage Δ
unit	63.58% <ø> (ø)

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

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0f1ad58...d558479. Read the comment docs.