str_util: remove Eq + PartialEq from StringPattern

I'm going to add regex support, and compiled Regex object isn't comparable.

lib/src/str_util.rs

@@ -38,7 +38,7 @@ fn parse_glob(src: &str) -> Result<glob::Pattern, StringPatternParseError> {
 
 /// Pattern to be tested against string property like commit description or
 /// branch name.
-#[derive(Clone, Debug, Eq, PartialEq)]
+#[derive(Clone, Debug)]
 pub enum StringPattern {
     /// Matches strings exactly.
     Exact(String),