fix fungibles::Inspect::balance

[wangjj9219]

fungibles::Inspect add a new function total_balance to return free+reserved, so balance should return the free balance

[codecov]

Codecov Report

Merging #926 (c4ed561) into master (56d66f6) will increase coverage by 0.05%.
The diff coverage is 92.85%.

@@            Coverage Diff             @@
##           master     #926      +/-   ##
==========================================
+ Coverage   78.32%   78.38%   +0.05%     
==========================================
  Files         105      105              
  Lines       10669    10701      +32     
==========================================
+ Hits         8357     8388      +31     
- Misses       2312     2313       +1     

Impacted Files	Coverage Δ
tokens/src/tests_events.rs	95.52% <ø> (ø)
tokens/src/lib.rs	77.72% <70.00%> (+0.03%)	⬆️
tokens/src/tests_fungibles.rs	99.11% <100.00%> (+0.11%)	⬆️

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