Revert "Update .NET 10 and 11 images with PowerShell v7.6.0-rc.1"

[lbussell]

Reverting because checksums did not match: https://dev.azure.com/dnceng/internal/_build/results?buildId=2911992&view=logs&j=fc59f0f2-c1bd-58ae-b870-833d1e8a924c&t=8d53baa0-ff68-5ea5-041a-af0e08303d7f&s=6884a131-87da-5381-61f3-d7acc3b91d76

Example failure:

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 > [stage-1 5/5] RUN powershell_version=7.6.0-rc.1     && wget --output-document PowerShell.Linux.Alpine.$powershell_version.nupkg https://powershellinfraartifacts-gkhedzdeaghdezhr.z01.azurefd.net/tool/$powershell_version/PowerShell.Linux.Alpine.$powershell_version.nupkg     && powershell_sha512='215af5d8160497bc184a16767f1b4a3a7f8c850c2dad0f36b17fb75286fc15433098649e6114c9f8f5470d66263c76f534275c3091a45410bf7c403da01e3f09'     && echo "$powershell_sha512  PowerShell.Linux.Alpine.$powershell_version.nupkg" | sha512sum -c -     && mkdir --parents /usr/share/powershell     && dotnet tool install --add-source / --tool-path /usr/share/powershell --version $powershell_version PowerShell.Linux.Alpine     && dotnet nuget locals all --clear     && rm PowerShell.Linux.Alpine.$powershell_version.nupkg     && ln -s /usr/share/powershell/pwsh /usr/bin/pwsh     && chmod 755 /usr/share/powershell/pwsh     && find /usr/share/powershell -print | grep -i '.*[.]nupkg$' | xargs rm     && apk add --no-cache ncurses-terminfo-base:
0.516 Connecting to powershellinfraartifacts-gkhedzdeaghdezhr.z01.azurefd.net (13.107.213.69:443)
0.540 saving to 'PowerShell.Linux.Alpine.7.6.0-rc.1.nupkg'
0.580 PowerShell.Linux.Alp 100% |********************************| 18.1M  0:00:00 ETA
0.580 'PowerShell.Linux.Alpine.7.6.0-rc.1.nupkg' saved
0.641 PowerShell.Linux.Alpine.7.6.0-rc.1.nupkg: FAILED
0.641 sha512sum: WARNING: 1 of 1 computed checksums did NOT match
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/cc @SeeminglyScience

I should have updated the PR again since more changes had been pushed to nightly before merging.