[MINOR] Use 7 chars instead of 10 for source build hash (#6858)

Signed-off-by: Simon Dudley <simon.dudley@consensys.net>

build.gradle

@@ -1020,7 +1020,7 @@ def calculateVersion() {
   } else {
     // If no version is supplied or it doesn't match the semantic versioning, calculate from git
     println("Generating project version as supplied is version not semver: ${project.version}")
-    def gitDetails = getGitCommitDetails(10) // Adjust length as needed
+    def gitDetails = getGitCommitDetails(7) // Adjust length as needed
     return "${gitDetails.date}-develop-${gitDetails.hash}"
   }
 }