op-deployer: Fix superchain proxy admin addr method

[mslipper]

Renames the ManagerOwnerAddrFor method to reflect what it actually does, and point it at the Sepolia proxy admin.

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 42.90%. Comparing base (d076e07) to head (149ac92).
Report is 3 commits behind head on develop.

Files with missing lines	Patch %	Lines
op-deployer/pkg/deployer/bootstrap/delayed_weth.go	0.00%	1 Missing ⚠️
op-deployer/pkg/deployer/state/intent.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #13361      +/-   ##
===========================================
- Coverage    47.21%   42.90%   -4.32%     
===========================================
  Files          937      771     -166     
  Lines        78191    68815    -9376     
  Branches       796        0     -796     
===========================================
- Hits         36916    29522    -7394     
+ Misses       38538    36780    -1758     
+ Partials      2737     2513     -224     

Flag	Coverage Δ
cannon-go-tests-32	?
cannon-go-tests-64	?
contracts-bedrock-tests	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
op-deployer/pkg/deployer/pipeline/init.go	59.40% <100.00%> (ø)
op-deployer/pkg/deployer/standard/standard.go	53.38% <100.00%> (-0.70%)	⬇️
op-deployer/pkg/deployer/bootstrap/delayed_weth.go	9.15% <0.00%> (ø)
op-deployer/pkg/deployer/state/intent.go	45.37% <0.00%> (ø)

... and 177 files with indirect coverage changes