docs: fix wacky markup bug caused by lack of sentence terminator

    <!-- The attribute that holds a Base64-encoded public key. -->

    <attr name="publicKey" format="string" />

    <!-- Attributes relating to a package verifier -->

    <!-- Attributes relating to a package verifier. -->

    <declare-styleable name="AndroidManifestPackageVerifier" parent="AndroidManifest">

        <!-- Specifies the Java-style package name that defines this

             package verifier. -->