patch 8.2.0488: Vim9: compiling can break when using a lambda inside :def

Problem:    Vim9: Compiling can break when using a lambda inside :def.
Solution:   Do not keep a pointer to the dfunc_T for longer time.
diff --git a/src/vim9.h b/src/vim9.h
index 7b95c37..a414caa 100644
--- a/src/vim9.h
+++ b/src/vim9.h
@@ -257,7 +257,7 @@
 // Functions defined with :def are stored in this growarray.
 // They are never removed, so that they can be found by index.
 // Deleted functions have the df_deleted flag set.
-garray_T def_functions = {0, 0, sizeof(dfunc_T), 200, NULL};
+garray_T def_functions = {0, 0, sizeof(dfunc_T), 50, NULL};
 #else
 extern garray_T def_functions;
 #endif