editors/featherpad: update to 1.2.0

Main changes:
- Try the file manager DBus interface when opening the containing folder
  (from the right-click menu of tab or side-pane item). In this way, it may be
  possible to select and scroll to the file.
- Restore the view position on reloading, as precisely as possible.
- Fixed searching in unusually large documents.
- Select the text between spaces with Ctrl + double click.
  (See Help → Multiple Clicks.)
- Added Rust syntax highlighting.
- Fixes and enhancement to XML and QML syntax highlighting.
- Bumped the minimum required version of Qt5 to 5.15.0.
- With Qt6, hide encodings that are not supported by Qt6.

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