[skip ci] Use more up-to-date wording for package managers

Most of the OSes Meson supports actually do have package managers,
and at least some of them are not harder to use than Linux ones.

docs/markdown/Wrap-dependency-system-manual.md

@@ -1,10 +1,8 @@
 # Wrap dependency system manual
 
 One of the major problems of multiplatform development is wrangling
-all your dependencies. This is easy on Linux where you can use system
-packages (and happen to know that your target distribution provides a
-recent enough version of the dependency) but awkward on other
-platforms. Most of those do not have a package manager at all. This
+all your dependencies. This is awkward on many platforms, especially
+on ones that do not have a built-in package manager. The latter problem
 has been worked around by having third party package managers. They
 are not really a solution for end user deployment, because you can't
 tell them to install a package manager just to use your app. On these