stop installing 'wheel' in wheel-building script (#1748)

We're now pre-installing `wheel` in the CI images: rapidsai/ci-imgs#215

This proposes removing a `pip install wheel` in CI here... fewer network requests = fewer random CI failures 😁

Authors:
  - James Lamb (https://github.com/jameslamb)

Approvers:
  - Bradley Dice (https://github.com/bdice)

URL: #1748

ci/build_wheel_cpp.sh

@@ -20,7 +20,6 @@ python -m pip wheel . -w dist -v --no-deps --disable-pip-version-check
 
 sccache --show-adv-stats
 
-python -m pip install wheel
 python -m wheel tags --platform any dist/* --remove
 
 ../../ci/validate_wheel.sh dist