chore(deps): update dependency system.collections.immutable to 9.0.9

[renovate]

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This PR contains the following updates:

Package	Change	Age	Confidence
System.Collections.Immutable (source)	9.0.8 -> 9.0.9

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Release Notes

dotnet/runtime (System.Collections.Immutable)

v9.0.9: .NET 9.0.9

Release

What's Changed

• [automated] Merge branch 'release/9.0' => 'release/9.0-staging' by @​github-actions[bot] in #​117671
• [release/9.0-staging] [Test Only] Fix BuildChainCustomTrustStore test by @​github-actions[bot] in #​117761
• [release/9.0-staging] Update dependencies from dotnet/arcade by @​dotnet-maestro[bot] in #​117742
• [release/9.0-staging] Update dependencies from dotnet/xharness by @​dotnet-maestro[bot] in #​117872
• [release/9.0-staging] Update dependencies from dotnet/sdk by @​dotnet-maestro[bot] in #​117873
• Revert "[release/9.0-staging] Update dependencies from dotnet/sdk" by @​lewing in #​118001
• [release/9.0-staging] Update dependencies from dotnet/cecil by @​dotnet-maestro[bot] in #​117910
• [release/9.0-staging] Update dependencies from dotnet/icu by @​dotnet-maestro[bot] in #​117962
• [release/9.0-staging] Update dependencies from dotnet/roslyn by @​dotnet-maestro[bot] in #​118080
• [release/9.0-staging] Update dependencies from dotnet/xharness by @​dotnet-maestro[bot] in #​118114
• [release/9.0-staging] Fix broken debugger/debuggee startup handshake protocol on macOS26. by @​github-actions[bot] in #​118212
• [release/9.0-staging] [NRBF] Allow the users to decode System.Nullable by @​github-actions[bot] in #​118328
• [release/9.0-staging] [Test Only] Disable/modify some TimeZoneInfoTests on Android by @​github-actions[bot] in #​118455
• Update branding to 9.0.9 by @​vseanreesermsft in #​118349
• Merging internal commits for release/9.0 by @​vseanreesermsft in #​118451
• [release/9.0-staging] Revert "Remove custom allocator." by @​github-actions[bot] in #​118279
• [release/9.0] Merge release/9.0-staging changes by @​krwq in #​118764
• [release/9.0] Update dependencies from dotnet/emsdk by @​dotnet-maestro[bot] in #​117879

Full Changelog: dotnet/runtime@v9.0.8...v9.0.9

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