Avoid PackageType in doctests

`PackageType` is only available with the `package-type` feature. So it's
best to avoid it in unrelated doctests. Otherwise, they will fail when
run without default features.

purl/src/builder.rs

@@ -10,11 +10,10 @@ use crate::{GenericPurl, ParseError, PurlParts, PurlShape, SmallString};
 /// # Example
 ///
 /// ```
-/// // `PurlBuilder` is an alias for `GenericPurlBuilder<PackageType>`.
-/// use purl::{PackageType, PurlBuilder};
+/// use purl::GenericPurlBuilder;
 ///
 /// // Use the builder if you want to set fields besides the type and name.
-/// let purl = PurlBuilder::new(PackageType::Maven, "my-package")
+/// let purl = GenericPurlBuilder::new(String::from("maven"), "my-package")
 ///     .with_namespace("my.company")
 ///     .build()
 ///     .unwrap();

purl/src/lib.rs

@@ -231,11 +231,13 @@ pub struct PurlParts {
 /// # Example
 ///
 /// ```
-/// // `Purl` is an alias for `GenericPurl<PackageType>`.
-/// use purl::{PackageType, Purl};
+/// use purl::GenericPurl;
 ///
 /// // Use the builder if you want to set fields besides the type and name.
-/// let purl = Purl::builder(PackageType::Npm, "my-package").with_version("1.2.3").build().unwrap();
+/// let purl = GenericPurl::builder(String::from("npm"), "my-package")
+///     .with_version("1.2.3")
+///     .build()
+///     .unwrap();
 ///
 /// assert_eq!("pkg:npm/[email protected]", &purl.to_string());
 /// ```