Fix slashes

Author: danmoseley

src/System.Runtime.Extensions/tests/System/IO/PathTests.cs

@@ -780,8 +780,8 @@ public static void GetFullPath_Windows_83Paths()
 
                     // Make sure the shortened name expands back to the original one
                     // Sometimes shortening or GetFullPath is changing the casing of "temp" on some test machines: normalize both sides
-                    tempFilePath = Regex.Replace(tempFilePath, @"\temp\\", @"\TEMP\\",  RegexOptions.IgnoreCase);
-                    shortName = Regex.Replace(Path.GetFullPath(shortName), @"\temp\\", @"\TEMP\\",  RegexOptions.IgnoreCase);
+                    tempFilePath = Regex.Replace(tempFilePath, @"\\temp\\", @"\TEMP\",  RegexOptions.IgnoreCase);
+                    shortName = Regex.Replace(Path.GetFullPath(shortName), @"\\temp\\", @"\TEMP\",  RegexOptions.IgnoreCase);
                     Assert.Equal(tempFilePath, shortName);
 
                     // Should work with device paths that aren't well-formed extended syntax