Align Maven version in system requirements with what is actually tested

See gh-26209

Author: zoosm3

spring-boot-project/spring-boot-docs/src/docs/asciidoc/getting-started.adoc

@@ -38,7 +38,7 @@ Explicit build support is provided for the following build tools:
 | Build Tool | Version
 
 | Maven
-| 3.3+
+| 3.5+
 
 | Gradle
 | 6 (6.3 or later). 5.6.x is also supported but in a deprecated form