bip54: make test vectors POSIX-compliant (newline at EOF)

This was pointed out during the Bitcoin Inquisition PR review

bip-0054/test_vectors/coinbases.json

@@ -77,3 +77,4 @@
         "comment": "Block at height 4 with coinbase's nLockTime set to block's nTime minus 1 and maximum non-final nSequence."
     }
 ]
+

bip-0054/test_vectors/sigops.json

@@ -1618,3 +1618,4 @@
         "valid": true
     }
 ]
+

bip-0054/test_vectors/timestamps.json

@@ -24251,3 +24251,4 @@
         "comment": "Block at height 4032 has a lower timestamp than block at height 2016."
     }
 ]
+

bip-0054/test_vectors/txsize.json

@@ -60,3 +60,4 @@
         "valid": false
     }
 ]
+