build: Use lower bounds for all 'docs' dependencies

* Loosen the install requirements for papermill, scrapbook, and
  sphinxcontrib-bibtex to use lower bounds instead of
  compatible release constraints.
* Required for PR https://github.com/scikit-hep/pyhf/pull/ 2444

pyproject.toml

@@ -107,16 +107,16 @@ test = [
     "pytest-mpl",
     "ipympl>=0.3.0",
     "pydocstyle",
-    "papermill~=2.5.0",
-    "scrapbook~=0.5.0",
+    "papermill>=2.5.0",
+    "scrapbook>=0.5.0",
     "jupyter",
     "graphviz",
     "pytest-socket>=0.2.0",  # c.f. PR #1917
 ]
 docs = [
     "pyhf[xmlio,contrib]",
     "sphinx>=7.0.0",  # c.f. https://github.com/scikit-hep/pyhf/pull/2271
-    "sphinxcontrib-bibtex~=2.1",
+    "sphinxcontrib-bibtex>=2.1",
     "sphinx-click",
     "sphinx-rtd-theme>=1.3.0",  # c.f. https://github.com/scikit-hep/pyhf/pull/2271
     "nbsphinx!=0.8.8",  # c.f. https://github.com/spatialaudio/nbsphinx/issues/620