Related to: JENKINS-14999

To use input parameter variable in "project name" of "copy artifacts from another project",
you must set proper read permission at upstream job.

At upstream job while working together with CloudBees Folders Plugin,
"Permission to Copy Artifact - Projects to allow copy artifacts"
display a misleading warning "Unable to find project: DOWNSTREAM_PROJECT_NAME"
when using DOWNSTREAM_PROJECT_NAME only without "FOLDERNAME" prefix.

When using full complete name together with FOLDER_NAME,
such as "FOLDERNAME/DOWNSTREAM_PROJECT_NAME",
"Permission to Copy Artifact - Projects to allow copy artifacts" will not display warning.
However,
the downstream job is unable to copy artifacts with error:

ERROR: Unable to find project for artifact copy: FOLDER_NAME/DOWNSTREAM_PROJECT_NAME
This may be due to incorrect project name or permission settings; see help for project name in job configuration.

If it's intended to use PROJECT_NAME only without full-name to include FOLDER_NAME,
then it should not display this misleading warning.
Also this note should put together with HELP string.