This reverts commit 3d17e19c2c.
The effect of turning off this setting is that mpv doesn't tell libass what
the video stream's resolution is. This happens to result in some files having
their transforms scaled in ways that give higher performance (as described
in #7435) because libass happened to guess a video resolution that resulted
in transforms yielding smaller bitmaps, but it's just as easy for the opposite
to happen depending on the resolutions and effects involved.
The option's name is also somewhat misleading: setting the storage size affects
blur, but it also affects stroke (which is far more important for the vast
majority of scripts) and 3D transforms (which look very screwy when done wrong).
4dcaf70b96