Regression issue: ESP Board Manager JSON file fails to load in Arduino IDE version 1.8.13 (but does work in 1.8.12)

I discovered that Arduino IDE 1.8.13 does not load the board manager file for ESP boards at https://dl.espressif.com/dl/package_esp32_index.json. After adding the URL in to Additional Board Manager URLs in Preferences and accessing the Board Manager dialog the system throws an error (appearing in the black error panel) "Error downloading https://dl.espressif.com/dl/package_esp32_index.json"

Performing the same test in 1.8.12, the board manager json file is loaded without error and ESP support libraries appear in the list.

Reproduce the failure by adding the ESP32 package URL in Arduino IDE 1.8.13 and opening Board Manager, then compare it with 1.8.12. The issue is resolved when https://dl.espressif.com/dl/package_esp32_index.json loads successfully and ESP support libraries appear in the list.

Written by the indexing model from the issue text.