Fix: Degrade severity level for IPA-125 rules (#581)

Author: yelizhenden-mdb

tools/spectral/ipa/rulesets/IPA-125.yaml

@@ -36,7 +36,7 @@ rules:
         This is valid because there are exactly 2 mappings for 2 oneOf references, and all values match.
 
     message: '{{error}} https://mdb.link/mongodb-atlas-openapi-validation#xgen-IPA-125-oneOf-must-have-discriminator'
-    severity: error
+    severity: warn
     given: '$.components.schemas[*]'
     then:
       function: 'IPA125OneOfMustHaveDiscriminator'
@@ -84,7 +84,7 @@ rules:
       ```
 
     message: '{{error}} https://mdb.link/mongodb-atlas-openapi-validation#xgen-IPA-125-oneOf-no-base-types'
-    severity: error
+    severity: warn
     given: '$.components.schemas[*]'
     then:
       function: 'IPA125OneOfNoBaseTypes'

tools/spectral/ipa/rulesets/README.md

@@ -508,7 +508,7 @@ Rules are based on [http://go/ipa/IPA-125](http://go/ipa/IPA-125).
 
 #### xgen-IPA-125-oneOf-must-have-discriminator
 
- ![error](https://img.shields.io/badge/error-red) 
+ ![warn](https://img.shields.io/badge/warning-yellow) 
 Each oneOf property must include a discriminator property to define the exact type.
 
 ##### Implementation details
@@ -538,7 +538,7 @@ Rule checks for the following conditions:
 
 #### xgen-IPA-125-oneOf-no-base-types
 
- ![error](https://img.shields.io/badge/error-red) 
+ ![warn](https://img.shields.io/badge/warning-yellow) 
 API producers should not use oneOf with base types like integer, string, boolean, or number.
 
 ##### Implementation details