Bump checkstyle from 8.9 to 8.18

Bumps [checkstyle](https://github.com/checkstyle/checkstyle) from 8.9 to 8.18.
- [Release notes](https://github.com/checkstyle/checkstyle/releases)
- [Commits](checkstyle/checkstyle@checkstyle-8.9...checkstyle-8.18)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

pom.xml

@@ -59,7 +59,7 @@
         <maven-gpg-plugin.version>1.6</maven-gpg-plugin.version>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <maven-checkstyle-plugin.version>3.0.0</maven-checkstyle-plugin.version>
-        <checkstyle.version>8.9</checkstyle.version>
+        <checkstyle.version>8.18</checkstyle.version>
         <checkstyle.dir.path>${basedir}/codingstyle</checkstyle.dir.path>
         <checkstyle.file.path>${checkstyle.dir.path}/soot_checkstyle_checks.xml</checkstyle.file.path>
         <checkstyle.failOnViolation>true</checkstyle.failOnViolation>