patch 8.2.2974: Greek spell checking uses wrong case folding

Problem:    Greek spell checking uses wrong case folding.
Solution:   Fold capital sigma depending on whether it is at the end of a
            word or not. (closes #299)
diff --git a/src/version.c b/src/version.c
index 25f2d15..99a635b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2974,
+/**/
     2973,
 /**/
     2972,