Mirror the recent EN-side updates in the Chinese External RAM guide:
- Replace "PSRAM 顶部" with "PSRAM 上端（最高物理地址区）" to match the
clarified wording on the EN side.
- Add the verification-helper pointer next to the heap_caps_malloc
example so Chinese readers also learn about esp_psram_ptr_is_no_enc().
Also drop the :cpp:func: cross-reference for esp_psram_ptr_is_no_enc on
the EN side: esp_psram.h is not in any chip-specific Doxyfile, so
Sphinx/Breathe cannot resolve the reference. Use a plain inline code
literal instead, matching the existing reference style for
esp_psram_get_size and other esp_psram functions in the docs.
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