Update springDocVersion to v2.8.4

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
org.springdoc:springdoc-openapi-starter-webmvc-ui (source)	2.8.3 -> 2.8.4
org.springdoc:springdoc-openapi (source)	2.8.3 -> 2.8.4

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Release Notes

springdoc/springdoc-openapi (org.springdoc:springdoc-openapi-starter-webmvc-ui)

v2.8.4

Added

• #​2873 - Improve performance of getGenericMapResponse
• #​2836 - Provide option to set allowed locales
• 2862 - Align Swagger-UI Prefix Path with Swagger-WebMvc Behavior

Changed

• Upgrade spring-boot to 3.4.2
• Upgrade spring-cloud-function to 4.2.1
• Upgrade swagger-core to 2.2.28

Fixed

• #​2870 - Springdoc 2.8.x + Spring Boot 3.4.1 breaks native image support
• #​2869 - Exception logged when generating schema for delete method of Spring Data repository.
• #​2856 - @​JsonUnwrapped is ignored in new version of lib.
• #​2852 - @​Schema(types = "xxx") does not work for multipart param with enabled springdoc.default-support-form-data config option.

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