Upgrade sphinx to fix docs build

[aabmass]

Upgrade sphinx to fix docs build which was failing with

docs-ci: commands[0]> make -C docs/ clean html    
make: Entering directory '/home/runner/work/opentelemetry-operations-python/opentelemetry-operations-python/docs'    
Running Sphinx v4.3.1    
    
Sphinx version error:    
The sphinxcontrib.applehelp extension used by this project needs at least Sphinx v5.0; it therefore cannot be built with this version.    
make: *** [Makefile:20: html] Error 2    
make: Leaving directory '/home/runner/work/opentelemetry-operations-python/opentelemetry-operations-python/docs'    
docs-ci: exit 2 (0.85 seconds) /home/runner/work/opentelemetry-operations-python/opentelemetry-operations-python> make -C docs/ clean html pid=1886    
docs-ci: FAIL code 2 (16.84=setup[15.99]+cmd[0.85] seconds)      
evaluation failed :( (17.38 seconds)