don't install pytest-codspeed on non x86_64 machines (#895)

tests/requirements.txt

@@ -4,7 +4,8 @@ hypothesis==6.79.4
 # pandas doesn't offer prebuilt wheels for all versions and platforms we test in CI e.g. aarch64 musllinux
 pandas==2.0.3; python_version >= "3.9" and python_version < "3.12" and implementation_name == "cpython" and platform_machine == 'x86_64'
 pytest==7.4.0
-pytest-codspeed~=2.1.0; implementation_name == "cpython"
+# we run codspeed benchmarks on x86_64 CPython (i.e. native github actions architecture)
+pytest-codspeed~=2.1.0; implementation_name == "cpython" and platform_machine == 'x86_64'
 pytest-examples==0.0.10
 pytest-speed==0.3.5
 pytest-mock==3.11.1