patch 8.1.0274: 'incsearch' triggers on ":source"

Problem:    'incsearch' triggers on ":source".
Solution:   Check for the whole command name.
diff --git a/src/version.c b/src/version.c
index 510ce45..8d02863 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    274,
+/**/
     273,
 /**/
     272,