vscode: remove default sourceExecutableName

generic.nix sets it to executableName by default if not set
if set, it prevents the correct sourceExecutableName being set for
-insiders

pkgs/applications/editors/vscode/vscode.nix

@@ -27,7 +27,6 @@ in
     version = "1.58.2";
     pname = "vscode";
 
-    sourceExecutableName = "code";
     executableName = "code" + lib.optionalString isInsiders "-insiders";
     longName = "Visual Studio Code" + lib.optionalString isInsiders " - Insiders";
     shortName = "Code" + lib.optionalString isInsiders " - Insiders";