chore(deps): update testcontainers-java monorepo to v1.21.0 (#1320)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

providers/flagd/pom.xml

@@ -147,13 +147,13 @@
         <dependency>
             <groupId>org.testcontainers</groupId>
             <artifactId>testcontainers</artifactId>
-            <version>1.20.6</version>
+            <version>1.21.0</version>
             <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>org.testcontainers</groupId>
             <artifactId>junit-jupiter</artifactId>
-            <version>1.20.6</version>
+            <version>1.21.0</version>
             <scope>test</scope>
         </dependency>
         <dependency>