Drop i686 support

In the next major update `pandas` will drop support for i686. This
package depends on `pandas`, thus it will need to stop building for i686
as well.

More information is available in Bugzilla:
https://bugzilla.redhat.com/show_bug.cgi?id=2263999

python-dask.spec

@@ -38,6 +38,10 @@ Patch:          0007-Ignore-NumPy-warnings-from-Pandas.patch
 # https://github.com/dask/dask/pull/10969
 Patch:          0008-TST-Add-missing-skip-for-pyarrow.patch
 
+# Stop building on i686
+# https://fedoraproject.org/wiki/Changes/EncourageI686LeafRemoval
+ExcludeArch:    %{ix86}
+
 %description
 Dask is a flexible parallel computing library for analytics.