Reverts "chore: turn on waitOnContentHash flag (#4706)" (#4708)

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Reverts: #4706
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Initiated by: jtmcdole
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Reason for reverting: I didn't push the new cocoon out tha towuld parse
this flag... whoops
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Original PR Author: jtmcdole
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Reviewed By: {matanlurey}
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This change reverts the following previous change:
Enable `waitOnContentHash` for the merge queue.

If something goes wrong; revert this PR and wait ~2 minutes.
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Co-authored-by: auto-submit[bot] <flutter-engprod-team@google.com>

Author: auto-submit[bot]

app_dart/config.yaml

@@ -4,8 +4,3 @@
 # app_dart/lib/src/service/config.dart
 
 backfillerCommitLimit: 50
-
-contentAwareHashing:
-  # This will cause PRs that enter the merge queue to wait on CAH hashing
-  # to happen before scheduling builds.
-  waitOnContentHash: true