Update the CMSSW version to CMSSW_10_6_29 from CMSSW_10_6_25.

standalone/.gitlab-ci.yml

-build_TreeMaker_cmssw_standalone_CMSSW_10_6_25:
+build_TreeMaker_cmssw_standalone_CMSSW_10_6_29:
     extends: .job_template
     variables:
-        CMSSW_VERSION: CMSSW_10_6_25
+        CMSSW_VERSION: CMSSW_10_6_29
         SCRAM_ARCH: slc7_amd64_gcc700
         BASE_IMAGE: clelange/cc7-cms:latest
         DOCKER_GROUP: treemaker