Update notebook outputs for SymPy 1.13 printing changes

[utiberious]

Problem

SymPy 1.13 changed two aspects of matrix printing, causing stored notebook outputs to diverge from current execution:

1. LaTeX: \begin{array}{cccc} → \begin{array}{} (column format specs removed)
2. Plain text: minor whitespace shift in unicode matrix pretty-printing (1-space indent change in some rows)

Affected notebooks: examples/ipython/gr_metrics.ipynb (Cells 16/19/21/23), examples/ipython/Old Format.ipynb (Cells 4/8/14).

These are cosmetic changes — the computed values are identical. nbval fails the cells because the stored outputs no longer match.

Fix

Re-execute the affected notebooks against SymPy 1.13 to refresh the stored outputs.