Remove rails binstubs from built gems

[tvdeyen]

The bin/rails script is solely used for local dev purposes. Since the default bindir from Rubygems is bin the binstub gets installed with the gems. This can cause issues with the rails command coming from rails itself.

Also removing the old script/rails files, which were excluded to solve the same issue.

[tvdeyen]

Excerpt from current solidus_legacy_promotions gem metadata file

--- !ruby/object:Gem::Specification
name: solidus_legacy_promotions
[...]
bindir: bin
[...]
files:
[..]
- bin/rails
[...]

which reveals that bindir is bin and bin/rails is included

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 89.54%. Comparing base (b1a3796) to head (dde8966). Report is 4 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #5917 +/- ## ======================================= Coverage 89.54% 89.54% ======================================= Files 783 783 Lines 17994 17994 ======================================= Hits 16113 16113 Misses 1881 1881 ```

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[github-actions[bot]]

💚 All backports created successfully

Status	Branch	Result
✅	v4.4

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