Bump gpbackup version to 1.0.0

Co-authored-by: NJamie McAtamney <jmcatamney@pivotal.io>
Co-authored-by: NChris Hajas <chajas@pivotal.io>

depends/conanfile_gpbackup.txt

 [requires]
-gpbackup/1.0.0-alpha.3@gpdb/stable
+gpbackup/1.0.0@gpdb/stable
 
 [imports]
 bin, * -> gpbackup/bin