Upgrade to Thymeleaf Spring5 3.0.6.M4

Closes gh-9208

spring-boot-dependencies/pom.xml

@@ -178,7 +178,7 @@
 		<statsd-client.version>3.1.0</statsd-client.version>
 		<sun-mail.version>${javax-mail.version}</sun-mail.version>
 		<thymeleaf.version>3.0.6.RELEASE</thymeleaf.version>
-		<thymeleaf-spring5.version>3.0.5.M3</thymeleaf-spring5.version>
+		<thymeleaf-spring5.version>3.0.6.M4</thymeleaf-spring5.version>
 		<thymeleaf-extras-springsecurity4.version>3.0.2.RELEASE</thymeleaf-extras-springsecurity4.version>
 		<thymeleaf-layout-dialect.version>2.2.1</thymeleaf-layout-dialect.version>
 		<thymeleaf-extras-data-attribute.version>2.0.1</thymeleaf-extras-data-attribute.version>