Update the Facebook secret key regex at signatures.yaml (#1000)

Author: rdimitrov

signatures.yaml

@@ -104,7 +104,7 @@
     - Page Access Token: (?i)(EAAG[0-9A-Za-z]{10,128})
     - Facebook Access Token: EAACEdEose0cBA[0-9A-Za-z]+
     - Facebook Client ID: (?i)(facebook|fb)(.{0,20})?['\"][0-9]{13,17}
-    - Facebook Secret Key: (?i)(facebook|fb)(.{0,20})?(?-i)['\"][0-9a-f]{32}
+    - Facebook Secret Key: (?i)(facebook|fb)(.{0,20})?['\"][0-9a-fA-F]{32}
     #- Client Token: (?i)fb[a-zA-Z0-9]{24,32}
     - Instagram Access Token: (?i)(IGQV[0-9A-Za-z-_]{10,255})
     - Instagram App Secret: (?i)(ig_[a-f0-9]{32})