Exclude some clocks on armv8 too

* See https://bugs.ruby-lang.org/issues/16234#note-16

spec/ruby/core/process/fixtures/clocks.rb

@@ -34,7 +34,7 @@ module ProcessSpecs
     end
 
     # These clocks in practice on ARM on Linux do not seem to match their reported resolution.
-    platform_is :armv7, :aarch64 do
+    platform_is :armv7, :armv8, :aarch64 do
       clocks = clocks.reject { |clock, value|
         [:CLOCK_PROCESS_CPUTIME_ID, :CLOCK_THREAD_CPUTIME_ID, :CLOCK_MONOTONIC_RAW].include?(clock)
       }