Bump System.Collections.Immutable from 5.0.0 to 7.0.0

Bumps [System.Collections.Immutable](https://github.com/dotnet/runtime) from 5.0.0 to 7.0.0.
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](https://github.com/dotnet/runtime/commits)

---
updated-dependencies:
- dependency-name: System.Collections.Immutable
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Discord Media Loader.Application/packages.config

@@ -10,7 +10,7 @@
   <package id="SharpRaven" version="2.4.0" targetFramework="net461" />
   <package id="SweetLib" version="0.2.1-alpha" targetFramework="net461" />
   <package id="System.Buffers" version="4.5.1" targetFramework="net461" />
-  <package id="System.Collections.Immutable" version="5.0.0" targetFramework="net461" />
+  <package id="System.Collections.Immutable" version="7.0.0" targetFramework="net461" />
   <package id="System.Linq" version="4.3.0" targetFramework="net461" requireReinstallation="true" />
   <package id="System.Linq.Async" version="4.1.1" targetFramework="net461" />
   <package id="System.Memory" version="4.5.4" targetFramework="net461" />

Discord Media Loader/packages.config

@@ -16,7 +16,7 @@
   <package id="Nito.Disposables" version="2.2.1" targetFramework="net461" />
   <package id="Octokit" version="0.50.0" targetFramework="net461" />
   <package id="System.Buffers" version="4.5.1" targetFramework="net461" />
-  <package id="System.Collections.Immutable" version="5.0.0" targetFramework="net461" />
+  <package id="System.Collections.Immutable" version="7.0.0" targetFramework="net461" />
   <package id="System.Linq" version="4.3.0" targetFramework="net461" />
   <package id="System.Memory" version="4.5.4" targetFramework="net461" />
   <package id="System.Numerics.Vectors" version="4.5.0" targetFramework="net461" />