ref-manual: Review edits to the PR variable in glossary.

Fixes [YOCTO #9843]

Some minor rewordings and removal of a stray comma.

(From yocto-docs rev: 9983619766bdb9d1a50948e219617aeef3170524)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/ref-variables.xml

@@ -9598,15 +9598,17 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
                     helps the package manager distinguish which package is the
                     most recent one in cases where many packages have the same
                     <filename>PV</filename> (i.e. <filename>PKGV</filename>).
-                    Packages have the same <filename>PV</filename> usually
-                    when the package manager installs the same upstream version
-                    and some of the packages include packaging fixes.
+                    A component having many packages with the same
+                    <filename>PV</filename> usually means that the packages all
+                    install the same upstream version, but with later
+                    (<filename>PR</filename>) version packages including
+                    packaging fixes.
                     <note>
                         <filename>PR</filename> does not need to be increased
                         for changes that do not change the package contents or
                         metadata.
                     </note>
-                    Because, manually managing <filename>PR</filename> can be
+                    Because manually managing <filename>PR</filename> can be
                     cumbersome and error-prone, an automated solution exists.
                     See the
                     "<ulink url='&YOCTO_DOCS_DEV_URL;#working-with-a-pr-service'>Working With a PR Service</ulink>"