Fix cddl spec for CostModels in Conway

[lehins]

Description

Fixing CDDL tests. CostModel deserialization was fixed, y making it stricter for PParamsUpdate in #3861

Received this error on CI: https://github.com/input-output-hk/cardano-ledger/actions/runs/6882361340/job/18720713406?pr=3874#step:15:4026

       Decoder error: Deserialisation failure while decoding GovAction (ConwayEra StandardCrypto).
       CBOR failed with error: DeserialiseFailure 41 "CMTooFewParamsError {cmTooFewExpected = 175, cmTooFewActual = 1}"

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated
• When applicable, versions are updated in .cabal and CHANGELOG.md files according to the
  versioning process.
• The version bounds in .cabal files for all affected packages are updated. If you change the bounds in a cabal file, that package itself must have a version increase. (See RELEASING.md)
• All visible changes are prepended to the latest section of a CHANGELOG.md for the affected packages. New section is never added with the code changes. (See RELEASING.md)
• Code is formatted with fourmolu (use scripts/fourmolize.sh)
• Cabal files are formatted (use scripts/cabal-format.sh)
• hie.yaml has been updated (use scripts/gen-hie.sh)
• Self-reviewed the diff

[teodanciu]

Makes sense, sorry for not catching this when I made the change.
Looks good to me