fix: bump jmeter version to 5.4.3 fixing critical Log4j vulnerabilities (#118)

CVE-2021-44228 and CVE-2021-45105, Jmeter changelog https://jmeter.apache.org/changes.html

Author: DaHoC

mqtt_jmeter/pom.xml

@@ -6,7 +6,7 @@
     <version>2.0.2</version>
 
     <properties>
-        <jmeter-version>5.0</jmeter-version>
+        <jmeter-version>5.4.3</jmeter-version>
     </properties>
 
     <dependencies>