Update C# version from 14.0 to 15.0 in releases.json (#10531)

* Update C# version from 14.0 to 15.0 in releases.json

* Update C# version from 14.0 to 15.0

Author: rbhanda

release-notes/11.0/preview/preview7/release.json

@@ -244,7 +244,7 @@
       "vs-mac-version": "",
       "vs-support": "",
       "vs-mac-support": "",
-      "csharp-version": "14.0",
+      "csharp-version": "15.0",
       "fsharp-version": "10.0",
       "vb-version": "17.13",
       "files": [
@@ -373,7 +373,7 @@
         "vs-mac-version": "",
         "vs-support": "",
         "vs-mac-support": "",
-        "csharp-version": "14.0",
+        "csharp-version": "15.0",
         "fsharp-version": "10.0",
         "vb-version": "17.13",
         "files": [
@@ -806,4 +806,4 @@
       ]
     }
   }
-}
+}

release-notes/11.0/releases.json

@@ -252,7 +252,7 @@
         "vs-mac-version": "",
         "vs-support": "",
         "vs-mac-support": "",
-        "csharp-version": "14.0",
+        "csharp-version": "15.0",
         "fsharp-version": "10.0",
         "vb-version": "17.13",
         "files": [
@@ -381,7 +381,7 @@
           "vs-mac-version": "",
           "vs-support": "",
           "vs-mac-support": "",
-          "csharp-version": "14.0",
+          "csharp-version": "15.0",
           "fsharp-version": "10.0",
           "vb-version": "17.13",
           "files": [
@@ -5399,4 +5399,4 @@
       }
     }
   ]
-}
+}