0.0.53 GUI does not maintain in fragment file the grammar via IMPORT_FROM_FILE

[gregshue]

When I used the GUI of Strictdoc 0.0.53 to add successive requirements in an sdoc fragment file the updated file now had the grammar inline instead of IMPORT_FROM_FILE. I had to manually replace the inline grammar with the reference before I could commit the file.

• My environment was Ubuntu 22.04 and interfacing through Firefox.
• I experienced this while creating this PR for Zephyr Project.

[stanislaw]

In the just-released 0.0.54a (installable with pip install strictdoc --pre), this should be working now.