Your image has strong compression artifacts, so even Heal Selection doesn't work too well. Just for the challenge, with out-of-the-box Gimp:
- Make a rectangular selection around the text. Selection top and bottom can be pretty close to the text, but left and right must have fairly wide margins (about the width of your widest horizontal bar, here the one in the T).
- Copy, Paste, Layer>To New layer
- Duplicate this new layer about 10 times
- Filters>Noise>Spread noise, uncouple H and V, use a high H (about the width of the T) and a small V (2-4 pixels).
- Repeat the filters on all these new layers (Select layer and Ctrl-F)
- Then put all these layers in "Lighten only" mode. Normally you shouldn't see any black dots, otherwise, redo with more layers. In practice, once all dots have disappeared, you can delete the excess layers...
- At that point on a good image your are done, but the technique makes the compression artifacts stand out
- So merge down, feather the selection and blur to taste.
Explication of the magic: "Spread noise" will randomly swap pixels, so among the 10 or so layers, any dark pixel from the letters has a very strong chance to be replaced at least once by a pixel from the neighboring background, and "Lighten only" mode selects that pixel.