The real source is `sympy-use-text.svg`.

The `sympy.svg` is "text to path" version of `sympy-use-text.svg`.
To create it from `sympy-use-text.svg` do (you have to install
the Computer Modern fonts first):

Inkscape
1. Run Inkscape.
2. Open `sympy-use-text.svg`
3. Ctrl-A
4. Shift-Ctrl-C
5. Save As `sympy.svg`
