docs: fix another regression in having functional docs

In commit 83a973ca04 a bunch of strange
changes were made, that were not even tested. Make sure people get the
correct command for running coverage targets.

docs/markdown/Commands.md

@@ -114,7 +114,7 @@ meson compile foo:shared_library foo:static_library bar
 Produce a coverage html report (if available):
 
 ```
-meson compile coverage-html
+ninja coverage-html
 ```
 
 ### dist

docs/markdown/howtox.md

@@ -174,7 +174,7 @@ Then issue the following commands.
 ```console
 $ meson compile
 $ meson test
-$ meson compile coverage-html (or coverage-xml)
+$ ninja coverage-html (or coverage-xml)
 ```
 
 The coverage report can be found in the meson-logs subdirectory.