Fix default StringHttpMessageConverter

[sonjih00n]

https://docs.spring.io/spring-boot/appendix/application-properties/index.html#application-properties.server.server.servlet.encoding.charset

Since the default value of server.servlet.encoding.charset is UTF-8, StringHttpMessageConverter with UTF-8 encoding is automatically created by the code below.

spring-boot/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/http/HttpMessageConvertersAutoConfiguration.java

Lines 79 to 86 in c1a7331

	@Bean
	@ConditionalOnMissingBean
	public StringHttpMessageConverter stringHttpMessageConverter(Environment environment) {
	Encoding encoding = Binder.get(environment).bindOrCreate("server.servlet.encoding", Encoding.class);
	StringHttpMessageConverter converter = new StringHttpMessageConverter(encoding.getCharset());
	converter.setWriteAcceptCharset(false);
	return converter;
	}

Therefore, HttpMessageConverters has two StringHttpMessageConverter as shown below.

So, StringHttpMessageConverter with ISO-8859-1 encoding is not used.
(Especially because the default value of server.servlet.encoding.charset is UTF-8)

Even if the developer sets ISO-8859-1 encoding according to the servlet default specification, There are two StringHttpMessageConverter using ISO-8859-1 encoding as shown below.

server.servlet.encoding.charset=ISO-8859-1

So, if there is an additional StringHttpMessageConverter, I would like to change it to not add the default StringHttpMessageConverter.

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[bclozel]

Build is failing. Please run the build before submitting PRs.
I think this is a duplicate of #21374 anyway - Spring Framework configures the default instance and Spring Boot contributes an additional one. While this might not be useful for the server-side case, message converters can be used in clients as well.

I'm declining this change as a result.