Minor: Add comment explaining why verify benchmark results uses relea…

…se mode (#7712)

While looking into #7709 I discovered why this test is run in release mode, and I wanted to leave a note for my future self

.github/workflows/rust.yml

@@ -241,6 +241,7 @@ jobs:
       - name: Verify that benchmark queries return expected results
         run: |
           export TPCH_DATA=`realpath datafusion/sqllogictest/test_files/tpch/data`
+          # use release build for plan verificaton because debug build causes stack overflow
           cargo test plan_q --package datafusion-benchmarks --profile release-nonlto --features=ci -- --test-threads=1
           INCLUDE_TPCH=true cargo test --test sqllogictests
       - name: Verify Working Directory Clean