docs: Remove :envvar: form spi_flash documentation

docs/en/api-reference/peripherals/spi_flash/index.rst

@@ -118,7 +118,7 @@ SPI Flash Size
 
 The SPI flash size is configured by writing a field in the software bootloader image header, flashed at offset 0x1000.
 
-By default, the SPI flash size is detected by ``esptool.py`` when this bootloader is written to flash, and the header is updated with the correct size. Alternatively, it is possible to generate a fixed flash size by setting :envvar:`CONFIG_ESPTOOLPY_FLASHSIZE` in the project configuration.
+By default, the SPI flash size is detected by ``esptool.py`` when this bootloader is written to flash, and the header is updated with the correct size. Alternatively, it is possible to generate a fixed flash size by setting :ref:`CONFIG_ESPTOOLPY_FLASHSIZE` in the project configuration.
 
 If it is necessary to override the configured flash size at runtime, it is possible to set the ``chip_size`` member of the ``g_rom_flashchip`` structure. This size is used by ``esp_flash_*`` functions (in both software & ROM) to check the bounds.
 

docs/zh_CN/api-reference/peripherals/spi_flash/index.rst

@@ -118,7 +118,7 @@ SPI flash 容量
 
 SPI flash 容量由引导加载程序镜像头部（烧录偏移量为 0x1000）的一个字段进行配置。
 
-默认情况下，引导程序被写入 flash 时，``esptool.py`` 会自动检测 SPI flash 容量，同时使用正确容量更新引导程序的头部。也可以在工程配置中设置 :envvar:`CONFIG_ESPTOOLPY_FLASHSIZE`，生成固定的 flash 容量。
+默认情况下，引导程序被写入 flash 时，``esptool.py`` 会自动检测 SPI flash 容量，同时使用正确容量更新引导程序的头部。也可以在工程配置中设置 :ref:`CONFIG_ESPTOOLPY_FLASHSIZE`，生成固定的 flash 容量。
 
 如需在运行时覆盖已配置的 flash 容量，请配置 ``g_rom_flashchip`` 结构中的 ``chip_size``。``esp_flash_*`` 函数使用此容量（于软件和 ROM 中）进行边界检查。