fix: remove some (broken) leftover from surface serialization

[thofma]

I guess we forgot to remove those after adding the proper database. Fixes the following bug:

julia> using Oscar
OSCAR 1.1.0-DEV  https://docs.oscar-system.org  Type "?Oscar" for help

julia> Oscar.R
Multivariate polynomial ring in 5 variables over GF(31991) graded by

[23792] signal (11.2): Segmentation fault: 11
in expression starting at none:0
fmpz_mat_entry at /bla/artifacts/f9bd64315b199a85cd681d69242b3cf75db9f49b/lib/libflint.dylib (unknown line)
jlplt_fmpz_mat_entry_9288 at /bla/compiled/v1.10/Hecke/lhBAK_0vvt3.dylib (unknown line)
Allocations: 18798613 (Pool: 18756078; Big: 42535); GC: 13
[1]    23792 segmentation fault  julia 

(The variable R was precompiled, but this is cannot work.)

[codecov]

Codecov Report

Merging #3545 (f205e1a) into master (d367722) will decrease coverage by 0.01%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3545      +/-   ##
==========================================
- Coverage   82.16%   82.16%   -0.01%     
==========================================
  Files         568      568              
  Lines       77055    77055              
==========================================
- Hits        63312    63311       -1     
- Misses      13743    13744       +1     

Files	Coverage Δ
src/AlgebraicGeometry/Surfaces/SurfacesP4.jl	14.81% <ø> (ø)

... and 1 file with indirect coverage changes