Bump BOLD truncation to 50 volumes for 36-parameter regression

25 volumes was too few: after discarding 2 TRs, only 23 timepoints
remained, which is fewer than the ~36 columns in the 36-parameter
nuisance regressor model, causing 3dTproject to fail.

Author: nx10

tests/integration/test_all.py

@@ -30,9 +30,10 @@
 _TASK = "balloonanalogrisktask"
 _RUN = "01"
 
-# Number of BOLD volumes to keep. Must be enough for nuisance regression
-# (after discarding --start-tr 2) but small enough to be fast.
-_BOLD_VOLUMES = 25
+# Number of BOLD volumes to keep. The 36-parameter regressor model needs
+# more timepoints than regressors (~36 columns + derivatives). After
+# discarding --start-tr 2, we need at least ~45 usable volumes.
+_BOLD_VOLUMES = 50
 
 
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