ICU-22721 Comment (back) some code generation method

Documented in docs/processes/release/tasks/updating-measure-unit.md,
updating the data for measurement units requires one to uncomment some code
in a unit test, run it, copy from stdout an paste in some other files.

That code is left enabled, spamming the stdandard output every time tests run.

icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/format/MeasureUnitTest.java

@@ -329,7 +329,7 @@ public class MeasureUnitTest extends CoreTestFmwk {
         //generateConstants("76"); // for MeasureUnit.java, update generated MeasureUnit constants
         //generateBackwardCompatibilityTest("76"); // for MeasureUnitTest.java, create TestCompatible74
         //generateCXXHConstants("76"); // for measunit.h, update generated createXXX methods
-        generateCXXConstants(); // for measunit.cpp, update generated code
+        //generateCXXConstants(); // for measunit.cpp, update generated code
         //generateCXXBackwardCompatibilityTest("74"); // for measfmttest.cpp, create TestCompatible74
         //updateJAVAVersions("74"); // for MeasureUnitTest.java, JAVA_VERSIONS
     }