Bump qs and govuk-prototype-kit

[dependabot]

Bumps qs and govuk-prototype-kit. These dependencies needed to be updated together.
Updates qs from 6.15.3 to 6.16.0

Changelog

Sourced from qs's changelog.

6.16.0

• [New] stringify: add a depth option to bound recursion depth (default Infinity)
• [Fix] stringify: serialize Date values when a filter is provided
• [Fix] parse: enforce arrayLimit on comma groups under []= when throwOnLimitExceeded is set
• [Fix] parse: flatten a collection appended to an overflowed array (#571)
• [Fix] utils: isBuffer: do not invoke a non-callable constructor.isBuffer
• [Fix] stringify: do not let allowEmptyArrays skip cycle detection (or drop own keys) on an empty array with own properties
• [Fix] stringify: encode dots in a top-level key with a primitive value when encodeDotInKeys is set (#562)
• [Docs] threat model: clarify stringify deep-nesting DoS is caller-bounded
• [Docs] clarify arrayLimit is a representation threshold, not an element-count cap
• [Tests] parse: remove a test that pinned []= comma groups escaping arrayLimit
• [Tests] stringify: pin current encodeDotInKeys separator-dot behavior
• [Dev Deps] update @ljharb/eslint-config, eslint
• [Dev Deps] update eslint, evalmd

Commits

• bb9379e v6.16.0
• 62fd254 [Fix] stringify: serialize Date values when a filter is provided
• 8859c37 [Fix] parse: enforce arrayLimit on comma groups under []= when `throwOn...
• 8079adc [Tests] parse: remove a test that pinned []= comma groups escaping `array...
• d56f48c [Fix] parse: flatten a collection appended to an overflowed array
• e83d321 [Fix] utils: isBuffer: do not invoke a non-callable constructor.isBuffer
• 7e87a07 [Dev Deps] update @ljharb/eslint-config, eslint
• 9a76af2 [Dev Deps] update eslint, evalmd
• 3a890d4 [Dev Deps] update eslint, evalmd
• b433a9b [Fix] stringify: do not let allowEmptyArrays skip cycle detection (or dro...
• Additional commits viewable in compare view

Updates govuk-prototype-kit from 13.20.2 to 13.20.4

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