fix: support x/collection migration on old chains

[0Tech]

Description

This patch would support old chains in which the default class ids start from 0.

related: #1105

Motivation and context

How has this been tested?

Screenshots (if appropriate):

Checklist:

• I followed the contributing guidelines and code of conduct.
• I have added a relevant changelog to CHANGELOG.md
• I have added tests to cover my changes.
• I have updated the documentation accordingly.
• I have updated API documentation client/docs/swagger-ui/swagger.yaml

[codecov]

Codecov Report

Merging #1106 (a7790c8) into rc/v0.48.0-rcx (0a27aef) will increase coverage by 0.01%.
The diff coverage is 100.00%.

Additional details and impacted files

@@                Coverage Diff                 @@
##           rc/v0.48.0-rcx    #1106      +/-   ##
==================================================
+ Coverage           69.75%   69.76%   +0.01%     
==================================================
  Files                 645      645              
  Lines               67468    67469       +1     
==================================================
+ Hits                47060    47068       +8     
+ Misses              18220    18213       -7     
  Partials             2188     2188              

Files Changed	Coverage Δ
x/collection/keeper/migrations/v2/store.go	88.29% <100.00%> (+6.57%)	⬆️

... and 1 file with indirect coverage changes

[zemyblue]

Could you add any unittest for this change?

[0Tech]

Could you add any unittest for this change?

Instead of adding a unit test, I've added a comment explaining the reason of the change.