Disable Stableswap

[mattverse]

Closes: #1503

What is the purpose of the change

The upcoming V9 upgrade should be including the gamm generalization, but not stable swap implementations.
This PR removes(comments out) stable swap inplementation and existing stableswap calls, which was to my surprise only present in msg_sever.go and module.go.

Brief Changelog

• Remove stableswap implementation from gamm module

Testing and Verifying

This change is a trivial rework / code cleanup without any test coverage.

Documentation and Release Note

• Does this pull request introduce a new feature or user-facing behavior changes? no
• Is a relevant changelog entry added to the Unreleased section in CHANGELOG.md? no
• How is the feature or change documented? (not applicable / specification (x/<module>/spec/) / Osmosis docs repo / not documented)

[codecov-commenter]

Codecov Report

Merging #1523 (597fab5) into main (f149135) will increase coverage by 0.03%.
The diff coverage is 36.04%.

@@            Coverage Diff             @@
##             main    #1523      +/-   ##
==========================================
+ Coverage   19.50%   19.54%   +0.03%     
==========================================
  Files         231      235       +4     
  Lines       31527    31598      +71     
==========================================
+ Hits         6150     6176      +26     
- Misses      24251    24293      +42     
- Partials     1126     1129       +3     

Impacted Files	Coverage Δ
x/gamm/keeper/msg_server.go	2.81% <ø> (-1.24%)	⬇️
x/gamm/module.go	64.10% <ø> (-2.57%)	⬇️
x/gamm/pool-models/balancer/amm.go	25.37% <0.00%> (+3.76%)	⬆️
x/gamm/pool-models/stableswap/amm.go	44.20% <0.00%> (-7.06%)	⬇️
x/gamm/pool-models/stableswap/pool.go	0.00% <0.00%> (ø)
osmoutils/binary_search.go	79.48% <79.48%> (ø)
osmoutils/cli_helpers.go	0.00% <0.00%> (ø)
osmoutils/cache_ctx.go	0.00% <0.00%> (ø)
osmoutils/dec_helper.go	0.00% <0.00%> (ø)

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[alexanderbez]

ACK. If stableswap was its own module, you wouldn't have to comment anything out -- you just exclude it from the modules list in app.go.

cc @ValarDragon