fix: Portal should not be initializable/upgradeable

[alainncls]

What does this PR do?

Prevents the portals from being initializable or upgradeable

Related ticket

Fixes #198

Type of change

• Chore
• Bug fix
• New feature
• Documentation update

Check list

• Unit tests for any smart contract change
• Contracts and functions are documented

[codecov-commenter]

Codecov Report

Merging #199 (32be69a) into dev (56d5ece) will decrease coverage by 0.14%.
Report is 1 commits behind head on dev.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              dev     #199      +/-   ##
==========================================
- Coverage   96.42%   96.29%   -0.14%     
==========================================
  Files          10       10              
  Lines         168      162       -6     
  Branches       40       40              
==========================================
- Hits          162      156       -6     
  Misses          4        4              
  Partials        2        2              

Files Changed	Coverage Δ
src/example/EASPortal.sol	92.85% <ø> (ø)
src/PortalRegistry.sol	95.83% <100.00%> (-0.17%)	⬇️
src/interface/AbstractPortal.sol	95.23% <100.00%> (-0.92%)	⬇️

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