Fix Text and icons overlapping in tool spec editor

[PiispaH]

The icons in Program files and Input & output files -widgets don't overlap with the texts anymore.

Fixes spine-tools/Spine-Toolbox#2160

Checklist before merging

• [x] Documentation (also in Toolbox repo) is up-to-date
• [x] Release notes in Toolbox repo have been updated
• [x] Unit tests have been added/updated accordingly
• [x] Code has been formatted by black
• [x] Unit tests pass

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (3d8820a) 54.88% compared to head (20f3edd) 54.88%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #134 +/- ## ======================================= Coverage 54.88% 54.88% ======================================= Files 192 192 Lines 17292 17292 Branches 2835 2835 ======================================= Hits 9490 9490 Misses 7311 7311 Partials 491 491 ``` | [Impacted Files](https://app.codecov.io/gh/spine-tools/spine-items/pull/134?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spine-tools) | Coverage Δ | | |---|---|---| | [...s/tool/widgets/tool\_specification\_editor\_window.py](https://app.codecov.io/gh/spine-tools/spine-items/pull/134?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spine-tools#diff-c3BpbmVfaXRlbXMvdG9vbC93aWRnZXRzL3Rvb2xfc3BlY2lmaWNhdGlvbl9lZGl0b3Jfd2luZG93LnB5) | `44.09% <100.00%> (ø)` | |

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