fix: sliding window exclusive end index

Author: suzyahyah

pandas/_libs/window/aggregations.pyx

@@ -442,7 +442,7 @@ def roll_var(const float64_t[:] values, ndarray[int64_t] start,
 
             # Over the first window, observations can only be added
             # never removed
-            if i == 0 or not is_monotonic_increasing_bounds or s <= end[i]:
+            if i == 0 or not is_monotonic_increasing_bounds or s < end[i]:
 
                 prev_value = values[s]
                 num_consecutive_same_value = 0

pandas/tests/window/test_rolling.py

@@ -1156,7 +1156,7 @@ def test_rolling_sem(frame_or_series):
 def test_rolling_var_correctness(func, values, window, ddof, expected_values):
     # GH: 37051, 42064, 54518, 52407, 47721
     ts = Series(values)
-    result = getattr(ts.rolling(window=window, center=True), func)(ddof=ddof)
+    result = getattr(ts.rolling(window=window), func)(ddof=ddof)
     if result.last_valid_index():
         result = result[
             result.first_valid_index() : result.last_valid_index() + 1