This removes the substring C:\Program Files (x86)\Git\bin; from the PATH string and re-assigns:
set PATH=%PATH:C:\Program Files (x86)\Git\bin;=%
You might use this to see the change:
echo %PATH:C:\Program Files (x86)\Git\bin;=% | tr ; \n
Note: be exact on the substring. It’s case-sensitive and slash-sensitive.
If you need to make it a persistent change use setx instead of set and open another console for changes to take effect.
setx /M PATH "%PATH:C:\Program Files (x86)\Git\bin;=%"