CI (Buildkite): increase the timeout of the code coverage job

[DilumAluthge]

No description provided.

[DilumAluthge]

Example scheduled build: https://buildkite.com/julialang/julia-master-scheduled/builds/321

[codecov]

Codecov Report

Merging #42994 (5c68e76) into master (b1cf46c) will increase coverage by 0.02%.
The diff coverage is 97.63%.

@@            Coverage Diff             @@
##           master   #42994      +/-   ##
==========================================
+ Coverage   89.44%   89.46%   +0.02%     
==========================================
  Files         343      343              
  Lines       79912    79994      +82     
==========================================
+ Hits        71475    71566      +91     
+ Misses       8437     8428       -9     

Impacted Files	Coverage Δ
base/Base.jl	49.31% <ø> (ø)
base/twiceprecision.jl	90.98% <ø> (ø)
stdlib/LinearAlgebra/src/dense.jl	99.29% <ø> (ø)
base/floatfuncs.jl	95.86% <95.83%> (+3.70%)	⬆️
base/compiler/ssair/passes.jl	93.03% <96.66%> (+0.93%)	⬆️
base/compiler/abstractinterpretation.jl	90.07% <100.00%> (+0.70%)	⬆️
base/compiler/optimize.jl	79.13% <100.00%> (+0.05%)	⬆️
base/mpfr.jl	89.27% <100.00%> (+0.18%)	⬆️
base/version.jl	90.34% <100.00%> (+5.45%)	⬆️
stdlib/LinearAlgebra/src/cholesky.jl	97.54% <100.00%> (+<0.01%)	⬆️
... and 47 more

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