Remove previously deprecated fields in cirq_google proto

[dstrain115]

• Removes schedule (not used in 5+ years)
• Removes gate and args (not used since v2.5, 3+ years)
• Removes checks on gate set and language.
• Removes tests that use the above.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.65%. Comparing base (2ad1b70) to head (7d41858).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7183      +/-   ##
==========================================
- Coverage   98.66%   98.65%   -0.01%     
==========================================
  Files        1106     1106              
  Lines       95914    95870      -44     
==========================================
- Hits        94630    94583      -47     
- Misses       1284     1287       +3     

☔ 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.

[wcourtney]

These fields are still used by Quantum Engine. Please see b/406240865 for more details and to track cleanup work.

[pavoljuhas]

LGTM for Cirq, please hold this for a green light from wcourtney.

PS: protofmt found some nits -

diff --git a/cirq-google/cirq_google/api/v2/program.proto b/cirq-google/cirq_google/api/v2/program.proto
index 7bc27788..d90ec97c 100644
--- a/cirq-google/cirq_google/api/v2/program.proto
+++ b/cirq-google/cirq_google/api/v2/program.proto
@@ -206,3 +206,3 @@ message Operation {
   // Previously deprecated fields.  Do not use.
-  reserved 1,2;
+  reserved 1, 2;
 
@@ -235,3 +235,3 @@ message Operation {
   // will only be populated in v2.5+
-  repeated Qubit qubits = 3 [deprecated=true];
+  repeated Qubit qubits = 3 [deprecated = true];
   repeated int32 qubit_constant_index = 6;

[dstrain115]

@wcourtney Are we good to submit this now?

[wcourtney]

Are we good to submit this now?

Yes, the uses of these protos have been removed and pushed to prod.