v2.2: Remove conditional feature as it is not supported (backport of #6577)

[mergify]

Problem

Adding dependencies based on configuration values is currently not supported. Cargo generates an error when trying to build this crate (see #6440 (comment))

https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#platform-specific-dependencies

The same applies to cfg(debug_assertions), cfg(test) and cfg(proc_macro). These values will not work as expected and will always have the default value returned by rustc --print=cfg. There is currently no way to add dependencies based on these configuration values.

Summary of Changes

Remove condition and add feature directly to dependency.

Fixes #

---

This is an automatic backport of pull request #6577 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 51c33c2 has failed:

On branch mergify/bp/v2.2/pr-6577
Your branch is up to date with 'origin/v2.2'.

You are currently cherry-picking commit 51c33c2f3.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   svm/Cargo.toml

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.4%. Comparing base (2b7a363) to head (a555a39).
⚠️ Report is 19 commits behind head on v2.2.

Additional details and impacted files

@@           Coverage Diff            @@
##             v2.2    #6606    +/-   ##
========================================
  Coverage    83.3%    83.4%            
========================================
  Files         807      807            
  Lines      373498   373498            
========================================
+ Hits       311484   311603   +119     
+ Misses      62014    61895   -119     

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