ci: remove windows

[PierreZ]

The FDB community is officially discontinuing the Windows build (see
apple/foundationdb#5135 for more info). We cannot download msi packages
as they were removed from official sites.

As the windows-latest is mandatory for any PR, this commit is removing
the windows-latest from Github actions. We may add it back later to
use community build.

[PierreZ]

Mmmh, I can see some errors related to clap. Clap's MSRV for >=3.0 is 1.54.0, should we bump?

Also, we are targetting structopt = "0.3.3" which does not exists, latest is 0.3.22.

[Speedy37]

bindingtester is only "in tree" so we probably don't have to care about MSRV.

[coveralls]

Coverage increased (+2.6%) to 70.049% when pulling 23dc27d on PierreZ:dev/remove-windows into f41fa13 on Clikengo:master.

[codecov]

Codecov Report

Merging #233 (23dc27d) into master (f41fa13) will increase coverage by 3.30%.
The diff coverage is n/a.

❗ Current head 23dc27d differs from pull request most recent head 54c76d2. Consider uploading reports for the commit 54c76d2 to get more accurate results

@@            Coverage Diff             @@
##           master     #233      +/-   ##
==========================================
+ Coverage   76.58%   79.88%   +3.30%     
==========================================
  Files          18       18              
  Lines        3041     3038       -3     
==========================================
+ Hits         2329     2427      +98     
+ Misses        712      611     -101     

Impacted Files	Coverage Δ
foundationdb-gen/src/lib.rs	0.42% <0.00%> (+<0.01%)	⬆️
foundationdb/src/tuple/mod.rs	89.78% <0.00%> (+0.86%)	⬆️
foundationdb-bindingtester/src/main.rs	90.24% <0.00%> (+1.55%)	⬆️
foundationdb/src/tuple/pack.rs	90.42% <0.00%> (+2.68%)	⬆️
foundationdb/src/api.rs	87.50% <0.00%> (+3.93%)	⬆️
foundationdb/src/tuple/element.rs	63.69% <0.00%> (+4.10%)	⬆️
foundationdb/src/future.rs	90.71% <0.00%> (+4.91%)	⬆️
foundationdb/src/database.rs	72.82% <0.00%> (+6.52%)	⬆️
foundationdb/src/transaction.rs	87.24% <0.00%> (+11.72%)	⬆️
foundationdb/src/tuple/versionstamp.rs	66.66% <0.00%> (+11.90%)	⬆️
... and 1 more

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[Speedy37]

but CI has (in the current configuration) to run with 1.40...

[PierreZ]

CI is green on my side, but I had to bump the MSRV to fix it, clang-sys's transitives dependencies requires 1.46.