Kotlin query collection format (#4248)

* Fixes incorrect query header collection constants

The OpenApi codegen converts OpenApi v2 documents into an OpenApi v3
representation. The query parameter collection formats are squeezed
into different values from the raw OpenApi 2 collection format values.
For example: csv -> space
See: DefaultCodegen#getCollectionFormat

* Updates kotlin samples

samples/client/petstore/kotlin-multiplatform/src/commonMain/kotlin/org/openapitools/client/infrastructure/ApiAbstractions.kt

@@ -5,8 +5,8 @@ typealias MultiValueMap = MutableMap<String,List<String>>
 fun collectionDelimiter(collectionFormat: String) = when(collectionFormat) {
     "csv" -> ","
     "tsv" -> "\t"
-    "pipes" -> "|"
-    "ssv" -> " "
+    "pipe" -> "|"
+    "space" -> " "
     else -> ""
 }