ci: use uv to install gcovr and sphinx

Change-Id: I1f04e20ef45f7352fddd4fdad7b7c418721a59ec
diff --git a/manpages/requirements.txt b/manpages/requirements.txt
new file mode 100644
index 0000000..6cfef5f
--- /dev/null
+++ b/manpages/requirements.txt
@@ -0,0 +1,2 @@
+docutils>=0.20
+sphinx>=7.0.1,<9