Fix test laplacian lambda max

[aurorarossi]

With this PR I added the seed for rand_graph.

[codecov[bot]]

Codecov Report

Merging #242 (55fd2b4) into master (1381a78) will increase coverage by 0.13%. The diff coverage is 93.75%.

@@            Coverage Diff             @@
##           master     #242      +/-   ##
==========================================
+ Coverage   88.29%   88.42%   +0.13%     
==========================================
  Files          16       16              
  Lines        1597     1624      +27     
==========================================
+ Hits         1410     1436      +26     
- Misses        187      188       +1     

Impacted Files	Coverage Δ
src/GNNGraphs/gnnheterograph.jl	85.91% <93.75%> (+4.09%)	:arrow_up:
src/GNNGraphs/transform.jl	96.55% <0.00%> (+0.43%)	:arrow_up:

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[CarloLucibello]

The problem this PR is trying to fix is the Laplacian test on nightly CI runs, e.g. here, right?

I don't know why that is happening but in principle computing the top eigenvalues of those rand bidirected graphs should not be problematic since their adjacency matrix is symmetric. Maybe zero-degree nodes cause some problems? Although I don't see why they should

[aurorarossi]

Yes and also in the function _eigmax there is the following line:

 KrylovKit.eigsolve(Symmetric(A), x0, 1, :LR)[1][1]

hence A is forced to be symmetric. When I run the tests on my computer they run smoothly (I have Julia 1.8).

[CarloLucibello]

So all this PR does is remove a test...