patch 8.2.4856: MinGW compiler complains about unknown escape sequence

Problem:    MinGW compiler complains about unknown escape sequence.
Solution:   Avoid using a backslash in path. (Christian Brabandt,
            closes #10337)
diff --git a/src/version.c b/src/version.c
index b10da45..fac7af9 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4856,
+/**/
     4855,
 /**/
     4854,