add-bugzilla-versions: Update the README.rst file

add-bugzilla-versions/README.rst

@@ -4,12 +4,10 @@ The script does the following:
 
 #.  For each project listed in :code:`add-bugzilla-versions/../modules.git`.
 
-    #.  Use CMake to extract the value of the
-        :code:`BUGZILLA_APPLICATION_VERSION` CMake variable.
+    #.  Use CMake to determine the project version, as defined by CMake’s project_
+        command.
 
-        The variable must be a cached string variable. For example::
-
-            set(BUGZILLA_APPLICATION_VERSION "2.3.4" CACHE STRING "" FORCE)
+        .. _project: https://cmake.org/cmake/help/latest/command/project.html#command:project
 
         If the variable is not found, the project is skipped.
 
@@ -23,10 +21,6 @@ To run the script:
         . venv/bin/activate
         pip install -r requirements.txt
 
-    Alternatively, you may install the Python modules listed in\
-    :code:`requirements.txt` globally in your system, using either your
-    package manager or pip, and run the script outside a virtual environment.
-
 #.  Run the script::
 
         python3 add-versions.py \