Tt 13476 update gw oas version (#6692)

https://github.com/TykTechnologies/tyk-analytics/pull/4281/files

## Description

Updates gateway OpenAPI version 

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## Motivation and Context

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## Types of changes

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- [ ] Bug fix (non-breaking change which fixes an issue)
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- [ ] Breaking change (fix or feature that would cause existing
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- [ ] Refactoring or add test (improvements in base code or adds test
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## Checklist

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- [ ] I ensured that the documentation is up to date
- [ ] I explained why this PR updates go.mod in detail with reasoning
why it's required
- [ ] I would like a code coverage CI quality gate exception and have
explained why

swagger.yml

@@ -1,7 +1,7 @@
 openapi: 3.0.0
 info:
   title: Tyk Gateway API
-  version: 5.3.0
+  version: 5.3.8
   description: |-
     The Tyk Gateway API is the primary means for integrating your application with the Tyk API Gateway system. This API is very small, and has no granular permissions system. It is intended to be used purely for internal automation and integration.