Update go-jsonnet to v0.22.0: v0.21.0 panics on super[<expr>] and crash-loops the server

### Summary

`v0.17.0` and current `main` pin `github.com/google/go-jsonnet v0.21.0`, which panics during static analysis on any file containing `super[e]` where `e` is not a plain variable reference. `DidOpen`/`DidChange` call `jsonnet.SnippetToAST` directly, so the panic kills the process. The client restarts the server, re-opens the same document, and it panics again — an unrecoverable crash loop that disables Jsonnet support for the whole workspace while such a file exists in it.

### Reproducer

```jsonnet
local f = { key: 'a' };
{ a: 1 } + { a: super[f.key] }
```

Opening this with vscode-jsonnet 0.7.4 kills the server on `didOpen`:

```
panic: Unexpected node
...
github.com/google/go-jsonnet/internal/program.analyzeVisit(...)
go-jsonnet@v0.21.0/internal/program/static_analyzer.go:155
...
github.com/grafana/jsonnet-language-server/pkg/server.(*Server).DidOpen(...)
pkg/server/server.go:117
```

### Root cause

In go-jsonnet v0.21.0 the desugarer's `*ast.SuperIndex` case never recurses into `node.Index`, so a computed index survives desugaring as a raw `ast.Index` with `Id` set and `Index == nil`. The static analyzer then reaches `case *ast.Index` -> `visitNext(a.Index, ...)` (`static_analyzer.go:106`) with that nil and falls through to `default: panic(...)` on line 155.

### Fix

Fixed upstream in google/go-jsonnet#849 (commit https://github.com/google/go-jsonnet/commit/fb23cdf1c07bce70525766fdf7b7518f4141fb1d), closing google/go-jsonnet#679, released in go-jsonnet v0.22.0 on 2026-03-24.

### The bump is clean

Verified on tag `v0.17.0` with `go mod edit -require=github.com/google/go-jsonnet@v0.22.0 && go mod tidy`:

- Compiles with no source changes; `go test ./...` fully passes.
- go.mod side effects are only the `go` directive moving to 1.24.5 (go-jsonnet v0.22.0 requires Go 1.24, which this repo already targets) and three transitive `golang.org/x/*` bumps.
- Verified end to end by driving both builds over stdio with `initialize` + `didOpen` of a file containing `super[e]`: the v0.21.0 build exits 2 with the panic above, the v0.22.0 build stays alive.

### Prior attempt

Renovate already opened #258 for this bump and it was autoclosed. The only failure reported there was a transient `go mod tidy` TLS timeout fetching the Go toolchain, not an incompatibility. That thread also has a user asking for v0.22.0 for the new numeric-underscore literals (`1_500_000`), which v0.21.0 rejects.