change git hash notation in NeXus release

Author: lukaspie

base_classes/NXroot.nxdl.xml

@@ -67,7 +67,7 @@
             The version of NeXus definitions used in writing the file. This can either be a date-based
             NeXus release (e.g., YYYY.MM), see https://github.com/nexusformat/definitions/releases or
             a version tag that includes additional development information, such as a commit distance and
-            a Git hash. This is typically formatted as  `vYYYY.MM.post1.dev<commit-distance>.g<git-hash>`,
+            a Git hash. This is typically formatted as  `vYYYY.MM.post1.dev<commit-distance>-g<git-hash>`,
             where `YYYY.MM` refers to the base version of the NeXus definitions. `post1.dev<commit-distance>` 
             indicates that the definitions are based on a commit after the base version (post1), with
             `<commit-distance>` being the number of commits since that version. `g<git-hash>` is the