patch 8.1.1974: Coverity warns for using pointer as array

Problem:    Coverity warns for using pointer as array.
Solution:   Call var2fpos() directly instead of using f_line().
diff --git a/src/version.c b/src/version.c
index c9860ac..3f92271 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1974,
+/**/
     1973,
 /**/
     1972,