ci: workaround docs build error

workaround for
https://github.com/readthedocs/sphinx_rtd_theme/issues/1343

build-appveyor.ps1

@@ -9,7 +9,7 @@ $env:Path += ";C:\Program Files\Git\usr\bin"
 py -m venv ericwtools-env
 Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser
 ericwtools-env\Scripts\Activate.ps1
-python.exe -m pip install sphinx_rtd_theme
+python.exe -m pip install -r docs/requirements.txt --force-reinstall
 
 # Confirm Sphinx is installed
 get-command sphinx-build

build-linux-64.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 
-python3 -m pip install sphinx_rtd_theme
+python3 -m pip install -r docs/requirements.txt --force-reinstall
 export PATH="~/.local/bin/:$PATH"
 
 BUILD_DIR=build-linux

build-osx.sh

@@ -3,7 +3,7 @@
 # for sha256sum, used by the tests
 brew install coreutils
 
-python3 -m pip install sphinx_rtd_theme
+python3 -m pip install -r docs/requirements.txt --force-reinstall
 
 BUILD_DIR=build-osx
 EMBREE_ZIP="https://github.com/embree/embree/releases/download/v3.13.0/embree-3.13.0.x86_64.macosx.zip"

build-windows.ps1

@@ -10,7 +10,7 @@ git submodule update --init --recursive
 py -m venv ericwtools-env
 Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser
 ericwtools-env\Scripts\Activate.ps1
-python.exe -m pip install sphinx_rtd_theme
+python.exe -m pip install -r docs/requirements.txt --force-reinstall
 
 # Confirm Sphinx is installed
 get-command sphinx-build

docs/requirements.txt

@@ -0,0 +1,2 @@
+sphinx==5.1.1
+sphinx_rtd_theme==1.0.0