Update build instructions to include a specific version for oapi-codegen

[kim-tsao]

Please specify the area for this PR

What does does this PR do / why we need it:
Updates the build instruction to specify the compatible version 1.12.4

Which issue(s) this PR fixes:

Fixes #?
devfile/api#1253

PR acceptance criteria:

• Test Coverage
  • Are your changes sufficiently tested, and are any applicable test cases added or updated to cover your changes? N/A

Documentation (WIP)

• Does the REST API doc need to be updated with your changes? N/A
• Does the registry library doc need to be updated with your changes?

How to test changes / Special notes to the reviewer:

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (049028b) 35.93% compared to head (58f8216) 35.93%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #183   +/-   ##
=======================================
  Coverage   35.93%   35.93%           
=======================================
  Files           7        7           
  Lines        1347     1347           
=======================================
  Hits          484      484           
  Misses        816      816           
  Partials       47       47           

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[michael-valdron]

I think this should refer to source generation.

Suggested change

	The current release relies on [oapi-codegen 1.12.4](https://github.com/deepmap/oapi-codegen/tree/v1.12.4). See the [Index Server README](index/server/README.md) for more information.
	The current release relies on [oapi-codegen 1.12.4](https://github.com/deepmap/oapi-codegen/tree/v1.12.4) for OpenAPI source generation. See the [Index Server README](index/server/README.md#source-generation) for more information.

[michael-valdron]

/lgtm

[openshift-ci]

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