Upgrade to Mimepull 1.9.12

Closes gh-18601

Author: wilkinsona

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

@@ -152,7 +152,7 @@
 		<lombok.version>1.18.10</lombok.version>
 		<mariadb.version>2.4.4</mariadb.version>
 		<micrometer.version>1.3.0</micrometer.version>
-		<mimepull.version>1.9.11</mimepull.version>
+		<mimepull.version>1.9.12</mimepull.version>
 		<mockito.version>3.1.0</mockito.version>
 		<mongo-driver-reactivestreams.version>1.12.0</mongo-driver-reactivestreams.version>
 		<mongodb.version>3.11.0</mongodb.version>