docs(source/snowflake): remove unsupported timeout field from reference

[anxkhn]

The Snowflake source Reference table documents a timeout field
(integer, "The connection timeout in seconds. Defaults to 60."), but the
Snowflake source has no such option:

• The Snowflake Config struct in internal/sources/snowflake/snowflake.go
  declares only name, type, account, user, password, database,
  schema, warehouse, and role. There is no timeout field, and
  initSnowflakeConnection never applies a connection timeout.
• Source configs are parsed with a strict YAML decoder (yaml.Strict() in
  internal/util/util.go), so an unknown key is a hard error, not a silently
  ignored no-op.

The net effect is that a user who follows the docs and adds timeout: 60 to a
Snowflake source config does not get a 60-second timeout: their configuration
fails to load with an unknown field "timeout" error. The documented option
actively breaks config loading.

This PR removes the fabricated timeout row from the reference table. The
warehouse and role rows are left untouched: those defaults ("COMPUTE_WH" /
"ACCOUNTADMIN") really are applied in initSnowflakeConnection, so the docs are
correct there.

It also adds a table-driven parse-failure case to TestFailParseFromYaml in
internal/sources/snowflake/snowflake_test.go asserting that a config with
timeout: 60 is rejected. This ties the doc change to observable behavior and
guards against the field being re-documented without being implemented.

Scope note: adding an actual connection timeout would be a feat; this PR is
the surgical docs fix that makes the reference match current behavior.

PR Checklist

• Make sure you reviewed CONTRIBUTING.md
• Make sure to open an issue as a bug/issue before writing your code!
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)
• Make sure to add ! if this involves a breaking change

Issue Reference

[gemini-code-assist]

Code Review

This pull request removes the unsupported timeout configuration parameter from the Snowflake source documentation and adds a unit test to verify that configuring a timeout field results in an unmarshaling error. I have no feedback to provide as there are no review comments.