[LNT] Fix get_sliding_runs of RunInfo

Summary:
Introduced by D37360. Make it sqlalchemy's Session instead of
flask.session.

Reviewers: cmatthews, hubert.reinterpretcast, kristof.beyls

Reviewed by: cmatthews

Differential Revision: https://reviews.llvm.org/D75891
diff --git a/lnt/server/ui/templates/v4_run.html b/lnt/server/ui/templates/v4_run.html
index 7350de8..c063f2d 100644
--- a/lnt/server/ui/templates/v4_run.html
+++ b/lnt/server/ui/templates/v4_run.html
@@ -313,7 +313,7 @@
       {% set field_index = ts.get_field_index(field) %}
       <section id="{{ field.name }}">
           {% set tests = [] %}
-          {% set (runs, compare_runs) = request_info.sri.get_sliding_runs(session, run, compare_to, request_info.num_comparison_runs) %}
+          {% set (runs, compare_runs) = request_info.sri.get_sliding_runs(request_info.session, run, compare_to, request_info.num_comparison_runs) %}
           {% for test_name,test_id in test_info %}
             {% set cr = request_info.sri.get_comparison_result(
                 runs, compare_runs, test_id, field, hash_field) %}