Compute embargo flag is switched after being manually updated

Reproduction steps:

• Import a github advisory
• Ensure all patched version are released
• Ensure the embargo date is computed automatically
• Edit the object to change the embargo date and switch off the compute embargo date flag
• Import again the advisory and trigger the scheduler to compute the embargo date

Expected result:

• The date is not modified

Obtained result:

• The flag to compute the embargo is removed and the embargo date is recomputed