🐛 Fix UTF-8 errror in configuration embed and retrieve (#23303)

The feature added in commit b464a4b1a4 introduced a UTF-8 encoding error for all users where UTF-8 is not the default codepage.

buildroot/share/PlatformIO/scripts/signature.py

 # headers.
 #
 def extract_defines(filepath):
-	f = open(filepath).read().split("\n")
+	f = open(filepath, encoding="utf8").read().split("\n")
 	a = []
 	for line in f:
 		sline = line.strip(" \t\n\r")