chore: add ctx to RevisionedReader.ReadSchema()

[miparnisari]

Description

Noticed in #2924 that spans were getting disconnected when experimental-schema-mode=read-new-write-new.

After this PR in merged, in https://github.com/josephschorr/spicedb/blob/3272cce5849c019a7df9f5d4241669f9d48df4b5/pkg/datalayer/schema_adapter.go#L340 we must remove the context.Background().

[codecov]

Codecov Report

❌ Patch coverage is 98.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 73.65%. Comparing base (3bbcb02) to head (dd4347b).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/services/v1/permissions_queryplan.go	0.00%	1 Missing ⚠️

❌ Your project status has failed because the head coverage (73.65%) is below the target coverage (75.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2952       +/-   ##
===========================================
+ Coverage   48.79%   73.65%   +24.87%     
===========================================
  Files         427      494       +67     
  Lines       54556    60626     +6070     
===========================================
+ Hits        26616    44651    +18035     
+ Misses      25225    12869    -12356     
- Partials     2715     3106      +391     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[josephschorr]

LGTM