feat!: remove deprecated std.prql_version

[prql-bot]

Summary

The deprecation notice for std.prql_version promised removal in PRQL 0.12.0, but we're now at 0.13.12 and the function was still present. Per maintainer feedback (@max-sixty), this PR removes the function rather than just updating the stale deprecation note.

prql.version has been the supported replacement since 0.11.1, so this is a breaking removal for any query still calling std.prql_version directly.

Found during the nightly survey of web/book/src/project/target.md.

Changes

• Drop std.prql_version from prqlc/prqlc/src/semantic/std.prql
• Remove the deprecation note from web/book/src/project/target.md
• Update debug-lineage snapshots where the removal shifted intrinsic IDs
• Add [unreleased] → Language CHANGELOG entry pointing users at prql.version

Test plan

• task prqlc:test passes
• prql.version still compiles (existing shortest_prql_version test covers this)
• Removing std.prql_version surfaces a normal "unknown name" error for any query that still calls it

[max-sixty]

let's instead remove it!

[prql-bot]

Done — pushed 40ecc1e. Dropped std.prql_version from std.prql and removed the deprecation note from target.md. prql.version is unaffected and all tests pass.

[prql-bot]

Self-review after switching approach on maintainer feedback. The code change itself is clean — std.prql_version is dropped, the deprecation note is removed from target.md, and the ID shifts propagate mechanically through the debug-lineage snapshots. No user-facing references to std.prql_version remain; the "prql_version" string in prqlc/prqlc/src/semantic/resolver/transforms.rs:442 is the intrinsic name still used by prql.version.

A few cleanup items before merge:

• PR title and body are stale. The title still reads docs: and the body says the function is "left in place" — both describe the first commit's approach. The second commit (feat: remove deprecated std.prql_version) is the final state. Since std.prql_version was documented and removing it will fail any query that still calls it, feat!: would more accurately signal the breaking removal.
• Missing CHANGELOG entry. [unreleased] → **Language** is empty. The 0.11.1 entry noted the deprecation, so the actual removal deserves a matching bullet pointing users at prql.version.

[prql-bot]

Addressed both self-review items in b57b779 and by updating the PR metadata:

• PR title → feat\!: to signal the breaking removal; body rewritten to describe the final state
• Added CHANGELOG [unreleased] → Language entry pointing users at prql.version