public/api-v2/issue-type/Invoke-JiraDeleteIssueType.ps1

#https://developer.atlassian.com/cloud/jira/platform/rest/v2/#api-rest-api-2-issuetype-id-delete
function Invoke-JiraDeleteIssueType {
    [CmdletBinding()]
    param (
        # The ID of the issue type
        [Parameter(Mandatory,Position=0)]
        [string]
        $IssueTypeId,

        # ID of an issue type to replace this issue type, if the deleted type is currently in use
        [Parameter(Position=1)]
        [string]
        $ReplacementId,

        # The JiraContext object to use for the request
        [Parameter()]
        [object]
        $JiraContext
    )
    process {
        $functionPath = "/rest/api/2/issuetype/$IssueTypeId"
        $verb = "DELETE"

        $query = New-PACRestMethodQueryParams
        if($PSBoundParameters.ContainsKey("ReplacementId")){$query.Add("alternativeIssueTypeId",$ReplacementId)}

        $method = New-PACRestMethod $functionPath $verb $query
        $method.Invoke($JiraContext)
    }
}