chore(pom.xml) cleanup markups to allow preparation of incremental builds

[dduportal]

Ref. jenkins-infra/helpdesk#3711 and closes jenkinsci/incrementals-tools#73

This PR cleans up the pom.xml to allow enablement of incrementals which requires an initial top-level version markup to be set following the (.+)-SNAPSHOT pattern.

It also removes duplicated markup in the properties section (as it will be updated by the initial incrementalify call).

Verification

From the HEAD of this PR, I was able to successully run the mvn incrementals:incrementalify command (using JDK11 and Maven 3.9.4) with the following result:

$ git status
On branch chore/fix-pom-to-enable-incremental
Your branch is ahead of 'upstream/main' by 1 commit.
  (use "git push" to publish your local commits)

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
        modified:   pom.xml

Untracked files:
  (use "git add <file>..." to include in what will be committed)
        .mvn/

no changes added to commit (use "git add" and/or "git commit -a")
$ git diff
diff --git a/pom.xml b/pom.xml
index 3da9837..05f8e6e 100644
--- a/pom.xml
+++ b/pom.xml
@@ -11,10 +11,13 @@
 
   <groupId>com.aq</groupId>
   <artifactId>accelq-ci-connect</artifactId>
-  <version>1.8-SNAPSHOT</version>
+  <version>${revision}${changelist}</version>
   <packaging>hpi</packaging>
 
   <properties>
+    <revision>1.8</revision>
+    <changelist>-SNAPSHOT</changelist>
+    <gitHubRepo>jenkinsci/accelq-ci-connect-plugin</gitHubRepo>
     <gitHubRepo>jenkinsci/accelq-ci-connect-plugin</gitHubRepo>
     <jenkins.version>2.401.3</jenkins.version>
     <java.level>11</java.level>
$ cat .mvn/extensions.xml 
<extensions xmlns="http://maven.apache.org/EXTENSIONS/1.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/EXTENSIONS/1.0.0 http://maven.apache.org/xsd/core-extensions-1.0.0.xsd">
  <extension>
    <groupId>io.jenkins.tools.incrementals</groupId>
    <artifactId>git-changelist-maven-extension</artifactId>
    <version>1.7</version>
  </extension>
</extensions>
$ cat .mvn/maven.config 
-Pconsume-incrementals
-Pmight-produce-incrementals