circleci: Disable spectests for arm64-native

[axic]

Fixes #829.

[codecov]

Codecov Report

Merging #831 (25b0eef) into master (5c5fae0) will decrease coverage by 0.79%.
The diff coverage is n/a.

❗ Current head 25b0eef differs from pull request most recent head e0e7b42. Consider uploading reports for the commit e0e7b42 to get more accurate results

@@            Coverage Diff             @@
##           master     #831      +/-   ##
==========================================
- Coverage   99.27%   98.47%   -0.80%     
==========================================
  Files          88        2      -86     
  Lines       13184      982   -12202     
==========================================
- Hits        13088      967   -12121     
+ Misses         96       15      -81     

Flag	Coverage Δ
rust	98.47% <ø> (ø)
spectests	?
unittests	?
unittests-32	?

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Impacted Files	Coverage Δ
test/utils/instantiate_helpers.hpp
test/unittests/execute_call_test.cpp
lib/fizzy/capi.cpp
test/unittests/end_to_end_test.cpp
test/unittests/execute_numeric_test.cpp
test/utils/adler32.hpp
lib/fizzy/exceptions.cpp
test/spectests/spectests.cpp
test/unittests/api_test.cpp
test/unittests/instantiate_test.cpp
... and 76 more