Give an example of how to use use-package+:vc without :rev

* doc/misc/use-package.texi (Install package): Add an example
block that doesn't use :rev, and instead shows that you can just
pass a URL as a string to :vc.

doc/misc/use-package.texi

@@ -1733,6 +1733,16 @@ that currently, you cannot upgrade built-in packages using @code{:vc}.
 
 For example,
 
+@example
+@group
+(use-package bbdb
+  :vc "https://git.savannah.nongnu.org/git/bbdb.git")
+@end group
+@end example
+
+will check out the latest release commit using
+@code{package-vc-install}, while
+
 @example
 @group
 (use-package bbdb
@@ -1741,8 +1751,8 @@ For example,
 @end group
 @end example
 
-would try -- by invoking @code{package-vc-install} -- to install the
-latest commit of the package @code{foo} from the specified remote.
+would try to install the latest commit of the package @code{foo} from
+the specified remote.
 
 @vindex use-package-vc-prefer-newest
 Alternatively, the @code{use-package-vc-prefer-newest} user option