Fixes validation for uri-template format

[nezhar]

Fixes the validation of uri-template using https://pypi.org/project/uri-template/

[codecov]

Codecov Report

Merging #819 (a0c3aae) into main (010d5e1) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #819   +/-   ##
=======================================
  Coverage   95.89%   95.89%           
=======================================
  Files          17       17           
  Lines        2584     2584           
  Branches      298      299    +1     
=======================================
  Hits         2478     2478           
+ Misses         87       86    -1     
- Partials       19       20    +1     

Impacted Files	Coverage Δ
jsonschema/_format.py	78.39% <100.00%> (+1.00%)	⬆️
jsonschema/tests/test_jsonschema_test_suite.py	87.50% <0.00%> (-5.00%)	⬇️

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[Julian]

Thanks!