Remove snapshot repo

Until we need to test docs-generator against a snapshot version, we want to avoid being spammed with pull requests to upgrade snapshot versions.

build.gradle

@@ -284,10 +284,6 @@ subprojects {
 	description = 'Documentation generator for Micrometer'
 
 	repositories {
-		maven {
-			url 'https://repo.spring.io/snapshot/'
-			content { includeGroup 'io.micrometer' }
-		}
 		mavenCentral()
 	}