[release] bump version to v4.4.39

- Update `version.txt` from "v" to v4.4.39
- Auto-synced `pkg/obioptions/version.go` via Makefile

pkg/obioptions/version.go

@@ -3,7 +3,7 @@ package obioptions
 // Version is automatically updated by the Makefile from version.txt
 // The patch number (third digit) is incremented on each push to the repository
 
-var _Version = "Release 4.4.38"
+var _Version = "Release 4.4.39"
 
 // Version returns the version of the obitools package.
 //

version.txt

@@ -1 +1 @@
-4.4.38
+4.4.39