deps: update dependency org.testcontainers:testcontainers-bom to v1.21.0 (#2016)

Author: renovate-bot

samples/spring-data-mybatis/pom.xml

@@ -42,7 +42,7 @@
       <dependency>
         <groupId>org.testcontainers</groupId>
         <artifactId>testcontainers-bom</artifactId>
-        <version>1.20.6</version>
+        <version>1.21.0</version>
         <scope>import</scope>
         <type>pom</type>
       </dependency>