pyproject.toml: prevent sphinxcontrib-qthelp incompatibilities

sphinxcontrib-qthelp>=1.0.4 depends on Sphinx>=5. This wasn't an issue
until now, since labgrid pins Sphinx==4.2.0 on stable. With
sphinxcontrib-qthelp>=1.0.6, this explicit dependency was dropped to
prevent cyclic dependencies, so the latest version gets installed,
although it's clearly incompatible. This is detected during runtime:

  The sphinxcontrib.qthelp extension used by this project needs at least Sphinx v5.0; it therefore cannot be built with this version.

So set sphinxcontrib-qthelp to a version lower than when the explicit
Sphinx dependency was dropped.

Signed-off-by: Bastian Krause <bst@pengutronix.de>

Author: Bastian-Krause

pyproject.toml

@@ -60,6 +60,7 @@ doc = [
     "sphinxcontrib-applehelp<1.0.8",
     "sphinxcontrib-devhelp<1.0.5",
     "sphinxcontrib-htmlhelp<2.0.4",
+    "sphinxcontrib-qthelp<1.0.6",
     "sphinx_rtd_theme==1.0.0",
 ]
 docker = ["docker==5.0.2"]
@@ -106,6 +107,7 @@ dev = [
     "sphinxcontrib-applehelp<1.0.8",
     "sphinxcontrib-devhelp<1.0.5",
     "sphinxcontrib-htmlhelp<2.0.4",
+    "sphinxcontrib-qthelp<1.0.6",
     "sphinx_rtd_theme==1.0.0",
 
     # labgrid[docker]