patch 8.2.1326: Vim9: skipping over white space after list

Problem:    Vim9: skipping over white space after list.
Solution:   Do not skip white space, a following [] would be misinterpreted.
            (closes #6552)  Fix a few side effects.
diff --git a/src/dict.c b/src/dict.c
index eedaf42..019227f 100644
--- a/src/dict.c
+++ b/src/dict.c
@@ -838,6 +838,10 @@
 		: eval1(arg, &tvkey, evalarg)) == FAIL)	// recursive!
 	    goto failret;
 
+	// The colon should come right after the key, but this wasn't checked
+	// previously, so only require it in Vim9 script.
+	if (!vim9script)
+	    *arg = skipwhite(*arg);
 	if (**arg != ':')
 	{
 	    if (evaluate)