Fix parent pom path

The path to the parent project of fc-tools/signer should be explicit to avoid errors like the one below:

➜  fc-service git:(main) ✗ mvn clean install -DskipTests
[INFO] Scanning for projects...
Downloading from central: https://repo.maven.apache.org/maven2/eu/xfsc/cat/fc-service/1.0.0.local/fc-service-1.0.0.local.pom
[ERROR] [ERROR] Some problems were encountered while processing the POMs:
[FATAL] Non-resolvable parent POM for eu.xfsc.cat:fc-tools-signer:${revision}: The following artifacts could not be resolved: eu.xfsc.cat:fc-service:pom:1.0.0.local (absent): Could not find artifact eu.xfsc.cat:fc-service:pom:1.0.0.local in central (https://repo.maven.apache.org/maven2) and 'parent.relativePath' points at wrong local POM @ line 7, column 13
[WARNING] 'build.plugins.plugin.version' for org.codehaus.mojo:license-maven-plugin is missing. @ eu.xfsc.cat:fc-service:1.0.0.local, /home/razvan/repo/stackable/fc-service/pom.xml, line 440, column 21
[WARNING] 'build.plugins.plugin.version' for org.codehaus.mojo:license-maven-plugin is missing. @ eu.xfsc.cat:fc-service:1.0.0.local, /home/razvan/repo/stackable/fc-service/pom.xml, line 440, column 21
[WARNING] 'build.plugins.plugin.version' for org.codehaus.mojo:license-maven-plugin is missing. @ eu.xfsc.cat:fc-service:1.0.0.local, /home/razvan/repo/stackable/fc-service/pom.xml, line 440, column 21
[WARNING] 'build.plugins.plugin.version' for org.codehaus.mojo:license-maven-plugin is missing. @ eu.xfsc.cat:fc-service:1.0.0.local, /home/razvan/repo/stackable/fc-service/pom.xml, line 440, column 21
[WARNING] 'build.plugins.plugin.version' for org.codehaus.mojo:license-maven-plugin is missing. @ eu.xfsc.cat:fc-service:1.0.0.local, /home/razvan/repo/stackable/fc-service/pom.xml, line 440, column 21
[WARNING] 'build.plugins.plugin.version' for org.codehaus.mojo:license-maven-plugin is missing. @ eu.xfsc.cat:fc-service:1.0.0.local, /home/razvan/repo/stackable/fc-service/pom.xml, line 440, column 21
[WARNING] 'build.plugins.plugin.version' for org.codehaus.mojo:license-maven-plugin is missing. @ line 440, column 21
 @ 
[ERROR] The build could not read 1 project -> [Help 1]
[ERROR]   
[ERROR]   The project eu.xfsc.cat:fc-tools-signer:${revision} (/home/razvan/repo/stackable/fc-service/fc-tools/signer/pom.xml) has 1 error
[ERROR]     Non-resolvable parent POM for eu.xfsc.cat:fc-tools-signer:${revision}: The following artifacts could not be resolved: eu.xfsc.cat:fc-service:pom:1.0.0.local (absent): Could not find artifact eu.xfsc.cat:fc-service:pom:1.0.0.local in central (https://repo.maven.apache.org/maven2) and 'parent.relativePath' points at wrong local POM @ line 7, column 13 -> [Help 2]