Fix a typo that resulted in skipping the wheel build preparing command step for Linux. (#318)

Author: AmineKhaldi

.github/workflows/build-wheels.yml

@@ -82,8 +82,7 @@ jobs:
           && echo "Building GMP"
           && cd gmp-6.2.1 && ./configure --enable-fat
           && make && make install && cd .. && rm -rf gmp-6.2.1
-        CIBW_BEFORE_BUID_LINUX: >
-          python -m pip install --upgrade pip
+        CIBW_BEFORE_BUILD_LINUX: python -m pip install --upgrade pip
         CIBW_ENVIRONMENT_MACOS: "MACOSX_DEPLOYMENT_TARGET=10.14"
         # GH hosted MacOS runner has gmp natively
         # CIBW_ARCHS_MACOS: x86_64 arm64 universal2