chore(docs): fix broken link in tm2/pkg/amino/README.md

[grepsuzette]

This is a broken link:

gno/tm2/pkg/amino/README.md

Lines 46 to 50 in 3f5a6ad

	## Amino in the Wild
	* Amino:binary spec in [Tendermint](
	https://github.com/tendermint/tendermint/blob/master/docs/spec/blockchain/encoding.md)

PR replaces it with the updated link.

Details

File was move there: https://github.com/tendermint/tendermint/blob/main/spec/blockchain/encoding.md

which says it's been moved there:
https://github.com/tendermint/tendermint/blob/main/spec/core/encoding.md

---

For the future, since we have a version in the monorepo and gnolang/tendermint2, where is the best place to post PR?

Because gnolang/tendermint2 of course has the same issue (https://github.com/gnolang/tendermint2/blob/master/pkgs/amino/README.md)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 54.60%. Comparing base (3f5a6ad) to head (6038701).
Report is 236 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2322      +/-   ##
==========================================
- Coverage   54.61%   54.60%   -0.02%     
==========================================
  Files         579      579              
  Lines       77899    77899              
==========================================
- Hits        42546    42535      -11     
- Misses      32182    32192      +10     
- Partials     3171     3172       +1     

Flag	Coverage Δ
tm2	54.44% <ø> (-0.05%)	⬇️

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