Fix metric name for chain state size

[yzang2019]

Describe your changes and provide context

This PR fixes a metric typo for iavl state size

Testing performed to validate your change

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 55.31%. Comparing base (b745c48) to head (d7a952c).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #517   +/-   ##
=======================================
  Coverage   55.31%   55.31%           
=======================================
  Files         631      631           
  Lines       54226    54226           
=======================================
+ Hits        29993    29996    +3     
+ Misses      22089    22087    -2     
+ Partials     2144     2143    -1     

Files	Coverage Δ
storev2/rootmulti/store.go	2.83% <0.00%> (ø)

... and 1 file with indirect coverage changes