Porter's Handbook: Document CARGO_USE_GITLAB

- Remove mention of CARGO_GH_CARGOTOML after ports r496795
- Update CARGO_USE_GITHUB description.  It does not patch Cargo.lock.
  That is done automatically during the configure phase by cargo
  itself and is not worth mentioning here.

Approved by:	mat
Differential Revision:	https://reviews.freebsd.org/D19697

en_US.ISO8859-1/books/porters-handbook/special/chapter.xml

@@ -997,21 +997,19 @@ CMAKE_OFF=	VAR3</programlisting>
 	      <entry><literal>no</literal></entry>
 	      <entry>Enable fetching of crates locked to specific Git
 		commits on GitHub via <varname>GH_TUPLE</varname>.
-		This will try to patch both
+		This will try to patch all
-		<filename>Cargo.lock</filename> and
+		<filename>Cargo.toml</filename> under
-		<filename>Cargo.toml</filename> to point to the
+		<varname>WRKDIR</varname> to point to the
 		offline sources instead of fetching them from a
-		Git repository during the build.  Use with caution
+		Git repository during the build.</entry>
-		as transitive Git dependencies are not resolved and
-		patched correctly.</entry>
 	    </row>
 
 	    <row>
-	      <entry><varname>CARGO_GH_CARGOTOML</varname></entry>
+	      <entry><varname>CARGO_USE_GITLAB</varname></entry>
-	      <entry><literal>${CARGO_CARGOTOML}</literal></entry>
+	      <entry><literal>no</literal></entry>
-	      <entry>List of <filename>Cargo.toml</filename> that
+	      <entry>Same as <varname>CARGO_USE_GITHUB</varname>
-		will be patched when using
+		but for GitLab instances and
-		<varname>CARGO_USE_GITHUB</varname>.</entry>
+		<varname>GL_TUPLE</varname>.</entry>
 	    </row>
 	  </tbody>
 	</tgroup>