Stop packaging Libtool `.la` files.

[pkgw]

Pursuant to https://github.com/conda-forge/staged-recipes/issues/673 and https://github.com/conda-forge/libxcb-feedstock/pull/9, we're going to remove these files from our packages. Eventually conda-build will do this automatically for us, but for now we take care of it manually. We need to delete the files both before the build (because inconsistent complements of .la files can break the build) and after because we may have installed new ones).

CC @jakirkham @mingwandroid @isuruf @ocefpaf @bgruening

• [x] Used a fork of the feedstock to propose changes
• [x] Bumped the build number (if the version is unchanged)
• [x] Re-rendered with the latest conda-smithy
• [x] Ensured the license file is being packaged.

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[bgruening]

Awesome! Thanks everyone!