Resolve artifacts from Maven Central first

- Use spring-build-conventions:0.0.36
- Add https://repo.spring.io/release to reference

Closes gh-1778

build.gradle

@@ -22,7 +22,7 @@ buildscript {
 	}
 
 	dependencies {
-		classpath 'io.spring.gradle:spring-build-conventions:0.0.35.RELEASE'
+		classpath 'io.spring.gradle:spring-build-conventions:0.0.36'
 		classpath "org.springframework.boot:spring-boot-gradle-plugin:$springBootVersion"
 	}
 }

spring-session-docs/spring-session-docs.gradle

@@ -65,3 +65,7 @@ asciidoctorj {
 			'highlightjsdir@': "js/highlight",
 			'docinfodir@': "."
 }
+
+repositories {
+    maven { url "https://repo.spring.io/release" }
+}