Fix typos in code and documentation

See gh-31734

spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/Restarter.java

@@ -327,7 +327,7 @@ public class Restarter {
 	}
 
 	private void cleanupKnownCaches() {
-		// Whilst not strictly necessary it helps to cleanup soft reference caches
+		// Whilst not strictly necessary it helps to clean up soft reference caches
 		// early rather than waiting for memory limits to be reached
 		ResolvableType.clearCache();
 		cleanCachedIntrospectionResultsCache();