Fix optional argument for fileOpen

Author: FileEX

functions/File/fileOpen.yaml

@@ -17,6 +17,7 @@ shared: &shared
     - name: 'readOnly'
       type: 'bool'
       description: By default, the file is opened with reading and writing access. You can specify true for this parameter if you only need reading access.
+      default: 'false'
   returns:
     description: If successful, returns a file handle for the file. Otherwise returns false (f.e. if the file doesn't exist).
     values: