Fix ref docs code snippet theme

This commit also fixes a link in the reference documentation.

See gh-18293

spring-boot-project/spring-boot-actuator-autoconfigure/pom.xml

@@ -758,7 +758,7 @@
 									<doctype>book</doctype>
 									<attributes>
 										<highlightjsdir>js/highlight</highlightjsdir>
-										<highlightjs-theme>atom-one-dark-reasonable</highlightjs-theme>
+										<highlightjs-theme>github</highlightjs-theme>
 										<linkcss>true</linkcss>
 										<imagesdir>./images</imagesdir>
 										<icons>font</icons>

spring-boot-project/spring-boot-docs/pom.xml

@@ -1573,7 +1573,7 @@
 									<doctype>book</doctype>
 									<attributes>
 										<highlightjsdir>js/highlight</highlightjsdir>
-										<highlightjs-theme>atom-one-dark-reasonable</highlightjs-theme>
+										<highlightjs-theme>github</highlightjs-theme>
 										<linkcss>true</linkcss>
 										<imagesdir>./images</imagesdir>
 										<icons>font</icons>

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

@@ -176,7 +176,7 @@ endif::[]
 
 TIP: The `spring-boot-starter-parent` is a great way to use Spring Boot, but it might not be suitable all of the time.
 Sometimes you may need to inherit from a different parent POM, or you might not like our default settings.
-In those cases, see <<using-boot-maven-without-a-parent>> for an alternative solution that uses an `import` scope.
+In those cases, see <<using-spring-boot.adoc#using-boot-maven-without-a-parent>> for an alternative solution that uses an `import` scope.
 
 
 

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/pom.xml

@@ -318,7 +318,7 @@
 									<doctype>book</doctype>
 									<attributes>
 										<highlightjsdir>js/highlight</highlightjsdir>
-										<highlightjs-theme>atom-one-dark-reasonable</highlightjs-theme>
+										<highlightjs-theme>github</highlightjs-theme>
 										<linkcss>true</linkcss>
 										<imagesdir>./images</imagesdir>
 										<icons>font</icons>