Remove aspnetcore source-build patch (#15213)

src/SourceBuild/patches/aspnetcore/0002-IDE0060-workaround.patch

@@ -1,22 +0,0 @@
-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
-From: MichaelSimons <msimons@microsoft.com>
-Date: Fri, 12 Aug 2022 23:02:54 +0000
-Subject: [PATCH] IDE0060 workaround
-
-Backport: https://github.com/dotnet/roslyn-analyzers/issues/6228
----
- src/Http/Routing/src/Matching/Ascii.cs | 1 -
- 1 file changed, 1 deletion(-)
-
-diff --git a/src/Http/Routing/src/Matching/Ascii.cs b/src/Http/Routing/src/Matching/Ascii.cs
-index 081af0bb07..393a9eb65f 100644
---- a/src/Http/Routing/src/Matching/Ascii.cs
-+++ b/src/Http/Routing/src/Matching/Ascii.cs
-@@ -12,7 +12,6 @@ internal static class Ascii
-     // and we know that the spans are the same length.
-     //
-     // Similar to https://github.com/dotnet/coreclr/blob/master/src/System.Private.CoreLib/shared/System/Globalization/CompareInfo.cs#L549
--    [MethodImpl(MethodImplOptions.AggressiveInlining)]
-     public static bool AsciiIgnoreCaseEquals(ReadOnlySpan<char> a, ReadOnlySpan<char> b, int length)
-     {
-         // The caller should have checked the length. We enforce that here by THROWING if the