Update cheatsheets

tldr/mp4decrypt

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+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# mp4decrypt
+
+> Decrypt an MP4 file.
+> Part of the Bento4 tools.
+> More information: <https://www.bento4.com/documentation/mp4decrypt/>.
+
+- Decrypt a file using a specific key (key ID in hex, key in hex):
+
+`mp4decrypt --key {{key_id_hex}}:{{key_hex}} {{path/to/input_file.mp4}} {{path/to/output_file.mp4}}`
+
+- Decrypt a file using a specific key for a track ID (track ID in decimal, key in hex):
+
+`mp4decrypt --key {{track_id}}:{{key_hex}} {{path/to/input_file.mp4}} {{path/to/output_file.mp4}}`
+
+- Decrypt a file using multiple keys while displaying the progress of the decryption:
+
+`mp4decrypt --key {{key_id_1}}:{{key_1}} --key {{key_id_2}}:{{key_2}} --show-progress {{path/to/input_file.mp4}} {{path/to/output_file.mp4}}`