With the Go 1.26 floor, golangci-lint's modernize analyzer (errorsastype)
flags the three errors.As calls that look for RequestBodyLimitError, which
turned the Lint workflow red on master after #8056. Replace them with the
generic errors.AsType; behavior is unchanged.
Assistance disclosure: this change was made by an AI agent (Claude Sonnet
5.5, model ID claude-sonnet-5-5) acting as Matthew Holt's agent and under
his approval. Build, go vet and the caddyhttp and caddyhttp/templates tests
pass locally; golangci-lint itself was not run locally.
Co-authored-by: Claude Code <noreply@anthropic.com>