HTTP/3: use max table capacity for insert buffer allocation

Previously, current capacity was used for the allocation, which could
be insufficient if table capacity was later increased.

src/http/v3/ngx_http_v3_table.c

@@ -159,13 +159,17 @@ ngx_buf_t *
 ngx_http_v3_get_insert_buffer(ngx_connection_t *c)
 {
     ngx_http_v3_session_t        *h3c;
+    ngx_http_v3_srv_conf_t       *h3scf;
     ngx_http_v3_dynamic_table_t  *dt;
 
     h3c = ngx_http_v3_get_session(c);
     dt = &h3c->table;
 
     if (dt->insert_buffer == NULL) {
-        dt->insert_buffer = ngx_create_temp_buf(c->pool, dt->capacity);
+        h3scf = ngx_http_v3_get_module_srv_conf(c, ngx_http_v3_module);
+
+        dt->insert_buffer = ngx_create_temp_buf(c->pool,
+                                                h3scf->max_table_capacity);
         if (dt->insert_buffer == NULL) {
             return NULL;
         }