Change camel case warning to upper camel case

Rust structs should be named in upper camel case aka PascalCase. "Upper camel case" was decided upon as the preferred phrase over PascalCase per: rust-lang/rfcs#2389

src/librustc_lint/nonstandard_style.rs

@@ -89,9 +89,9 @@ impl NonCamelCaseTypes {
         if !is_camel_case(name) {
             let c = to_camel_case(&name.as_str());
             let m = if c.is_empty() {
-                format!("{} `{}` should have a camel case name such as `CamelCase`", sort, name)
+                format!("{} `{}` should have an upper camel case name such as `CamelCase`", sort, name)
             } else {
-                format!("{} `{}` should have a camel case name such as `{}`", sort, name, c)
+                format!("{} `{}` should have an upper camel case name such as `{}`", sort, name, c)
             };
             cx.span_lint(NON_CAMEL_CASE_TYPES, span, &m);
         }