BIP374: update reference.py and secp256k1.py to be executable #1736

1. 
   jonatack commented at 4:42 pm on December 31, 2024: member

   by adding to each a python shebang and changing their file permissions from 644 to 755, as mentioned in #1734 (comment).

   These files don’t need to be executable in order to run gen_test_vectors.py and run_test_vectors.py but it is helpful to allow developers to invoke them directly.

   Before:

   0$ ./reference.py 
   1zsh: permission denied: ./reference.py
   

   After:

   0$ ./reference.py 
   

2. bip374: update reference.py to be executable a261439d92
3. bip374: update secp256k1.py to be executable cce668de3c
4. andrewtoth approved
5. 
   andrewtoth commented at 7:00 pm on January 1, 2025: contributor

   ACK cce668de3c48a28d489c38ab41bbb7a6e1700eed
6. jonatack merged this on Jan 2, 2025
7. jonatack closed this on Jan 2, 2025

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8. jonatack deleted the branch on Jan 2, 2025

Contributors
jonatack andrewtoth