Fix minimalMavenBuildVersion to 3.9.8

Just checking for 3.9 is not good enough. Property session.rootDirectory
was introduced only in 3.9.2. So require 3.9.8.

pom.xml

@@ -81,7 +81,7 @@
     <properties>
         <minimalJavaBuildVersion>17</minimalJavaBuildVersion>
         <surefireJdk>[${minimalJavaBuildVersion},)</surefireJdk>
-        <minimalMavenBuildVersion>3.9</minimalMavenBuildVersion>
+        <minimalMavenBuildVersion>3.9.8</minimalMavenBuildVersion>
 
         <format.impsort.action>sort</format.impsort.action>
         <format.formatter.action>format</format.formatter.action>