deps: require regex-syntax 0.6.14

This brings in the bug fix for #640 for flag scoping.

Author: BurntSushi

Cargo.toml

@@ -121,7 +121,7 @@ optional = true
 # For parsing regular expressions.
 [dependencies.regex-syntax]
 path = "regex-syntax"
-version = "0.6.12"
+version = "0.6.14"
 default-features = false
 
 [dev-dependencies]