patch 8.2.2757: Vim9: blob tests for legacy and Vim9 script are separate

Problem:    Vim9: blob tests for legacy and Vim9 script are separate.
Solution:   Add CheckLegacyAndVim9Success().  Make blob index assign work.
diff --git a/src/version.c b/src/version.c
index 0dc382f..3728f32 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2757,
+/**/
     2756,
 /**/
     2755,