Declare formatter version to avoid spotless choosing a version

diffplug/spotless#2503 (comment)
indicates that spotless chooses a formatter version based on the JDK
running the formatting process.  The spotless maintainer recommends that
we declare a formatter version explicitly so that the formatter won't
change based on the JDK version.

Testing done:

In this repository:

mvn clean install versions:display-plugin-updates

In the winstone repository (where we saw the issue):

Reverted the change that made the formatting independent of Java version
in b95111923002d82598d4d85f67f40fa6170dda5e and then added explicit
spotless version definition to the pom file so that I could confirm that
changing Java versions does not change the formatting.

MarkEWaite/winstone@78ea965
has the details

. ~/bin/use_java17
mvn spotless:apply
git status

. ~/bin/use_java21
mvn spotless:apply
git status

Matching pull request in plugin pom:

* jenkinsci/plugin-pom#1151

Author: MarkEWaite

pom.xml

@@ -649,7 +649,11 @@
             <indent>
               <spaces>true</spaces>
             </indent>
-            <palantirJavaFormat />
+            <palantirJavaFormat>
+              <!-- Declare version so that spotless does not choose a version based on JDK version -->
+              <!-- https://github.com/diffplug/spotless/issues/2503#issuecomment-2953146277 -->
+              <version>2.67.0</version>
+            </palantirJavaFormat>
             <removeUnusedImports />
             <trimTrailingWhitespace />
           </java>