Don't show Failed to Import popup after overwriting the file on server once

[isc-vgao]

This fixes #264.

Testing Steps:

1. In git-source-control repo, checkout overwrite-server-popup branch

git checkout overwrite-server-popup

2. In VS Code, click the ObjectScript icon in the left side menu to open ObjectScript Explorer window, click "Choose Server and Namespace" and sign in using InterSystems Server Credentials.
3. Load git-source-control into the current namespace

zpm "load <path to local git-source-control repo cloned in step 1>"

4. Modify a file you haven't overwritten on server
5. Save the file you modified in step 3. Verify that "Failed to import" VS Code popup shows up on the first time you modify and save the file.
6. Click "Overwrite on Server"
7. Modify file from step 3 and save the file. Verify that "Failed to import" VS Code popup no longer shows up.
8. Undo changes to file you modified.