patch 8.2.2552: Vim9: no reason to consider "{{{{{{{{" a command

Problem:    Vim9: no reason to consider "{{{{{{{{" a command.
Solution:   Just use "{". (issue #7904)
diff --git a/src/ex_cmds.h b/src/ex_cmds.h
index 7888d6f..d114fed 100644
--- a/src/ex_cmds.h
+++ b/src/ex_cmds.h
@@ -1819,7 +1819,7 @@
 EXCMD(CMD_at,		"@",		ex_at,
 	EX_RANGE|EX_WHOLEFOLD|EX_EXTRA|EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK|EX_NONWHITE_OK,
 	ADDR_LINES),
-EXCMD(CMD_block,	"{{{{{{{{",	ex_block,  // not found normally
+EXCMD(CMD_block,	"{",		ex_block,  // not found normally
 	0,
 	ADDR_NONE),
 EXCMD(CMD_endblock,	"}",		ex_endblock,