Remove check for deprecated configuration properties

See gh-20528

Author: snicoll

spring-boot-project/spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -2200,7 +2200,7 @@ Nowadays, Content Negotiation is much more reliable.
 There are other ways to deal with HTTP clients that don't consistently send proper "Accept" request headers.
 Instead of using suffix matching, we can use a query parameter to ensure that requests like `"GET /projects/spring-boot?format=json"` will be mapped to `@GetMapping("/projects/spring-boot")`:
 
-[source,properties,indent=0,subs="verbatim,quotes,attributes",configprops]
+[source,properties,indent=0,subs="verbatim,quotes,attributes"]
 ----
 	spring.mvc.contentnegotiation.favor-parameter=true
 
@@ -2214,15 +2214,15 @@ Instead of using suffix matching, we can use a query parameter to ensure that re
 Suffix pattern matching is deprecated and will be removed in a future release.
 If you understand the caveats and would still like your application to use suffix pattern matching, the following configuration is required:
 
-[source,properties,indent=0,subs="verbatim,quotes,attributes",configprops]
+[source,properties,indent=0,subs="verbatim,quotes,attributes"]
 ----
 	spring.mvc.contentnegotiation.favor-path-extension=true
 	spring.mvc.pathmatch.use-suffix-pattern=true
 ----
 
 Alternatively, rather than open all suffix patterns, it's more secure to just support registered suffix patterns:
 
-[source,properties,indent=0,subs="verbatim,quotes,attributes",configprops]
+[source,properties,indent=0,subs="verbatim,quotes,attributes"]
 ----
 	spring.mvc.contentnegotiation.favor-path-extension=true
 	spring.mvc.pathmatch.use-registered-suffix-pattern=true