Fix typo in KotlinClientCodegen.java user-visible error message (#17674)

Author: neeme-praks-sympower

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java

@@ -771,7 +771,7 @@ private void processJvmSpringWebClientLibrary(final String infrastructureFolder)
 
     private void processJvmSpringRestClientLibrary(final String infrastructureFolder) {
         if (additionalProperties.getOrDefault(USE_SPRING_BOOT3, false).equals(false)) {
-            throw new RuntimeException("This library muse use spring boot 3. Try adding '--additional-properties useSpringBoot3=true' to your command.");
+            throw new RuntimeException("This library must use Spring Boot 3. Try adding '--additional-properties useSpringBoot3=true' to your command.");
         }
 
         proccessJvmSpring(infrastructureFolder);