Tweak version linter max_depth

[psteckler]

Lower the version linter max_depth to 9 (was 12). That's the depth of the type shapes, as S-expressions, used when comparing them across branches. The type shapes are truncated to that depth, so that differences in contained types are elided, avoiding false positives.

Tested by running the script locally with edited type shape files. Changes tried:

• change to built-in type (should give error)
• change to variant constructor (should give error)
• change to record field name (should give error)
• change to record field name in contained type (should not give error)

A depth of 10 gave an error for the last case. Backing off to 9 removed the generated error.

There may still be occasional false positives. For example, a contained type might be simpler than a record, such as a built-in type or variant, for instance. Those should be infrequent, and easy enough to spot, because the change to the contained type will also generate an error.

In fact, the truncation code wasn't working, because the type shape was not converted to an S-expression. Fixed here.

Added the --no-clobber option to wget, so that the type shape file is not downloaded if it exists (which it did with repeated local testing).

Closes #14232.

[psteckler]

!ci-build-me

[psteckler]

!ci-build-me

[mrmr1993]

!approved-for-mainnet