opm migrate: add help text note about concatenated json format

[joelanford]

Signed-off-by: Joe Lanford joe.lanford@gmail.com

Description of the change:
Update opm migrate help text to explain that json output format produces concatenated JSON

Motivation for the change:
Concatenated JSON may come as a surprise to users, because not all tools/libraries support it.

Reviewer Checklist

• Implementation matches the proposed design, or proposal is updated to match implementation
• Sufficient unit test coverage
• Sufficient end-to-end test coverage
• Docs updated or added to /docs
• Commit messages sensible and descriptive

[codecov]

Codecov Report

Merging #1055 (4500b04) into master (0080ea0) will increase coverage by 0.04%.
The diff coverage is 70.37%.

❗ Current head 4500b04 differs from pull request most recent head 08a7d9f. Consider uploading reports for the commit 08a7d9f to get more accurate results

@@            Coverage Diff             @@
##           master    #1055      +/-   ##
==========================================
+ Coverage   52.06%   52.10%   +0.04%     
==========================================
  Files         102      102              
  Lines        9218     9244      +26     
==========================================
+ Hits         4799     4817      +18     
- Misses       3505     3513       +8     
  Partials      914      914              

Impacted Files	Coverage Δ
alpha/declcfg/load.go	76.52% <70.37%> (-2.13%)	⬇️

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[everettraven]

/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: everettraven, joelanford

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• OWNERS [joelanford]

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[everettraven]

/lgtm-remove

(didn't think it would still add the LGTM label even though I am not in the OWNERS file)

[everettraven]

/lgtm cancel

[everettraven]

Whoops ... I didn't mean to make it auto-merge and was too late with the cancel command it seems. At least this was a minor update 😅