.Net: Remove the Functions.Markdown package (#11951)

### Motivation, Context and Description

This PR removes the Functions.Markdown project and, as a result, stops
publishing it as a NuGet package. This is part of a clean-up initiative
due to the lack of usage of the package.

Contributes to:
#10070

Author: SergeyMenshykh

dotnet/SK-dotnet.sln

@@ -183,8 +183,6 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "PromptTemplates.Handlebars"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Functions.Yaml", "src\Functions\Functions.Yaml\Functions.Yaml.csproj", "{4AD4E731-16E7-4A0E-B403-6C96459F989B}"
 EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Functions.Markdown", "src\Functions\Functions.Markdown\Functions.Markdown.csproj", "{E576E260-4030-4C4C-B207-CA3B684E9669}"
-EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Planners.Handlebars", "src\Planners\Planners.Handlebars\Planners.Handlebars.csproj", "{352DAE69-E31C-44E3-A35F-E0342A955869}"
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "planning", "planning", "{A7DAB812-81CF-4931-B38C-468A3261C4C8}"
@@ -769,12 +767,6 @@ Global
 		{4AD4E731-16E7-4A0E-B403-6C96459F989B}.Publish|Any CPU.Build.0 = Publish|Any CPU
 		{4AD4E731-16E7-4A0E-B403-6C96459F989B}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{4AD4E731-16E7-4A0E-B403-6C96459F989B}.Release|Any CPU.Build.0 = Release|Any CPU
-		{E576E260-4030-4C4C-B207-CA3B684E9669}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{E576E260-4030-4C4C-B207-CA3B684E9669}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{E576E260-4030-4C4C-B207-CA3B684E9669}.Publish|Any CPU.ActiveCfg = Publish|Any CPU
-		{E576E260-4030-4C4C-B207-CA3B684E9669}.Publish|Any CPU.Build.0 = Publish|Any CPU
-		{E576E260-4030-4C4C-B207-CA3B684E9669}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{E576E260-4030-4C4C-B207-CA3B684E9669}.Release|Any CPU.Build.0 = Release|Any CPU
 		{352DAE69-E31C-44E3-A35F-E0342A955869}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{352DAE69-E31C-44E3-A35F-E0342A955869}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{352DAE69-E31C-44E3-A35F-E0342A955869}.Publish|Any CPU.ActiveCfg = Publish|Any CPU
@@ -1577,7 +1569,6 @@ Global
 		{8B62C632-9D70-4DC1-AEAB-82D057A09A19} = {24503383-A8C4-4255-9998-28D70FE8E99A}
 		{B0646036-0C50-4F66-B479-ADA9C1166816} = {078F96B4-09E1-4E0E-B214-F71A4F4BF633}
 		{4AD4E731-16E7-4A0E-B403-6C96459F989B} = {9ECD1AA0-75B3-4E25-B0B5-9F0945B64974}
-		{E576E260-4030-4C4C-B207-CA3B684E9669} = {9ECD1AA0-75B3-4E25-B0B5-9F0945B64974}
 		{352DAE69-E31C-44E3-A35F-E0342A955869} = {A21FAC7C-0C09-4EAD-843B-926ACEF73C80}
 		{A7DAB812-81CF-4931-B38C-468A3261C4C8} = {4D3DAE63-41C6-4E1C-A35A-E77BDFC40675}
 		{3F4E0DC5-2241-4EF2-9F69-E7EC7834D349} = {A7DAB812-81CF-4931-B38C-468A3261C4C8}

dotnet/src/Functions/Functions.UnitTests/Functions.UnitTests.csproj

@@ -67,7 +67,6 @@
     <ProjectReference Include="..\..\Connectors\Connectors.AzureOpenAI\Connectors.AzureOpenAI.csproj" />
     <ProjectReference Include="..\..\SemanticKernel.Core\SemanticKernel.Core.csproj" />
     <ProjectReference Include="..\Functions.Grpc\Functions.Grpc.csproj" />
-    <ProjectReference Include="..\Functions.Markdown\Functions.Markdown.csproj" />
     <ProjectReference Include="..\Functions.OpenApi.Extensions\Functions.OpenApi.Extensions.csproj" />
     <ProjectReference Include="..\Functions.OpenApi\Functions.OpenApi.csproj" />
     <ProjectReference Include="..\Functions.Yaml\Functions.Yaml.csproj" />