chore: change metadata field type byte to string

[atheeshp]

Description

ref: #10490
comment

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Author Checklist

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

I have...

• included the correct type prefix in the PR title
• added ! to the type prefix if API or client breaking change
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• followed the guidelines for building modules
• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
• included comments for documenting Go code
• updated the relevant documentation or specification
• reviewed "Files changed" and left comments if necessary
• confirmed all CI checks have passed

Reviewers Checklist

All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.

I have...

• confirmed the correct type prefix in the PR title
• confirmed ! in the type prefix if API or client breaking change
• confirmed all author checklist items have been addressed
• reviewed state machine logic
• reviewed API design and naming
• reviewed documentation is accurate
• reviewed tests and test coverage
• manually tested (if applicable)

[codecov]

Codecov Report

Merging #11269 (e08ad18) into master (9a87557) will decrease coverage by 0.08%.
The diff coverage is 63.41%.

@@            Coverage Diff             @@
##           master   #11269      +/-   ##
==========================================
- Coverage   66.02%   65.93%   -0.09%     
==========================================
  Files         665      661       -4     
  Lines       68595    68379     -216     
==========================================
- Hits        45291    45088     -203     
+ Misses      20664    20650      -14     
- Partials     2640     2641       +1     

Impacted Files	Coverage Δ
x/gov/client/cli/tx.go	14.89% <ø> (ø)
x/gov/keeper/msg_server.go	6.57% <0.00%> (ø)
x/gov/types/v1beta2/proposal.go	15.62% <0.00%> (ø)
x/group/types.go	46.26% <ø> (ø)
x/gov/client/cli/parse.go	65.71% <25.92%> (-22.29%)	⬇️
x/group/msgs.go	53.92% <50.00%> (ø)
client/tx/factory.go	26.66% <60.00%> (+2.02%)	⬆️
store/rootmulti/store.go	75.52% <100.00%> (+0.18%)	⬆️
x/gov/keeper/proposal.go	77.84% <100.00%> (ø)
x/gov/simulation/operations.go	85.31% <100.00%> (ø)
... and 14 more