gitignore: Fix pattern for .vscode/ directories
gitignore: Fix pattern for .vscode/ directories

The vscode documentation[1] says that the editor use a directory
named ".vscode", not "+.vscode".

".vscode" is also what the original commit[2] in pull request 100[3]
contained.

However, commit e9fafcd89d3e88767670800f684c58eee727b84f
probably contained a cut and paste error and added the
ignore pattern for directories called "+.vscode".

  [1]: https://code.visualstudio.com/docs/editor/workspaces
  [2]: https://github.com/gphoto/libgphoto2/pull/100/commits/d8ff05da8cf5c4790c6e8f0dd4dda34b382ec585
  [3]: https://github.com/gphoto/libgphoto2/pull/100

gphoto/libgphoto2,gphoto/libgphoto2,gphoto/libgphoto2,gphoto/libgphoto2,gphoto/libgphoto2,gphoto/libgphoto2