[hft]: Fix conditional mark in high frequency telemetry test (sonic-net#21482)

What is the motivation for this PR?
Wrong condition for skipping HFT test

How did you do it?
Correct it as described in this comment: sonic-net#20379 (comment)

Signed-off-by: Ze Gan <ganze718@gmail.com>

Author: Pterosaur

tests/common/plugins/conditional_mark/tests_mark_conditions.yaml

@@ -3174,8 +3174,7 @@ high_frequency_telemetry:
     reason: "High frequency telemetry isn't supported in this platform"
     conditions_logical_operator: or
     conditions:
-      - "'nvidia_sn5600' not in platform"
-      - "'nvidia_sn5640' not in platform"
+      - "platform not in ['x86_64-nvidia_sn5600-r0', 'x86_64-nvidia_sn5640-r0', 'x86_64-arista_7060x6_64pe_b']"
 
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