Update try-flagr url

[zhouzhuojie]

Description

Update try-flagr url to be https://try-flagr.onrender.com

Motivation and Context

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

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Legend

[codecov-commenter]

Codecov Report

Merging #552 (1a3402a) into main (acddd31) will not change coverage.
The diff coverage is n/a.

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@@           Coverage Diff           @@
##             main     #552   +/-   ##
=======================================
  Coverage   81.07%   81.07%           
=======================================
  Files          28       28           
  Lines        2256     2256           
=======================================
  Hits         1829     1829           
  Misses        337      337           
  Partials       90       90           

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