fix: fixed build issue in flash encryption example with certain config

Addresses a build failure that occurs when flash encryption is enabled with default configurations.

The build failure did not manifest in the CI environment because the configuration
CONFIG_SECURE_FLASH_REQUIRE_ALREADY_ENABLED is set in sdkconfig.ci.
This configuration is responsible for reducing the bootloader size.

Closes https://github.com/espressif/esp-idf/issues/12619

examples/security/flash_encryption/sdkconfig.defaults

@@ -2,4 +2,4 @@
 CONFIG_PARTITION_TABLE_CUSTOM=y
 CONFIG_PARTITION_TABLE_CUSTOM_FILENAME="partitions_example.csv"
 CONFIG_PARTITION_TABLE_FILENAME="partitions_example.csv"
-CONFIG_PARTITION_TABLE_OFFSET=0x9000
+CONFIG_PARTITION_TABLE_OFFSET=0xD000