Bump version to 3.0.8

Due to our (new) convention plugins inherit their versions from the
OpenProject core. The next stable release of the OpenProject core is
3.0.8.

CHANGELOG.md

@@ -1,6 +1,6 @@
 # Changelog
 
-## 1.0.0
+## 3.0.8
 ## 1.0.0.pre5
 
 * `#2561` [Work package tracking] Internal error when exporting work package list with cost columns to excel

lib/open_project/xls_export/version.rb

@@ -1,5 +1,5 @@
 module OpenProject
   module XlsExport
-    VERSION = "1.0.0"
+    VERSION = "3.0.8"
   end
 end