Pin sphinx-rtd-theme to <2 to revert update to pre-release version

Due to a bug in poetry ( python-poetry/poetry#8194 ),
the 2.0.0rc2 pre-release of sphinx-rtd-theme was selected to allow
the update of docutils to 0.19, instead of sticking with the current
version for both.
This breaks the doc build with this error:

```
writing output... [  0%] admin/apache

Theme error:
An error happened in rendering the page admin/apache.
Reason: AttributeError("'str' object has no attribute 'attributes'")
```

lib/galaxy/dependencies/dev-requirements.txt

@@ -32,7 +32,7 @@ cycler==0.11.0 ; python_version >= "3.7" and python_version < "3.12"
 darker==1.7.2 ; python_version >= "3.7" and python_version < "3.12"
 defusedxml==0.7.1 ; python_version >= "3.7" and python_version < "3.12"
 deprecated==1.2.14 ; python_version >= "3.7" and python_version < "3.12"
-docutils==0.19 ; python_version >= "3.7" and python_version < "3.12"
+docutils==0.18.1 ; python_version >= "3.7" and python_version < "3.12"
 exceptiongroup==1.1.3 ; python_version >= "3.7" and python_version < "3.12"
 filelock==3.12.2 ; python_version >= "3.7" and python_version < "3.12"
 fluent-logger==0.10.0 ; python_version >= "3.7" and python_version < "3.12"
@@ -134,7 +134,7 @@ six==1.16.0 ; python_version >= "3.7" and python_version < "3.12"
 sniffio==1.3.0 ; python_version >= "3.7" and python_version < "3.12"
 snowballstemmer==2.2.0 ; python_version >= "3.7" and python_version < "3.12"
 sortedcontainers==2.4.0 ; python_version >= "3.7" and python_version < "3.12"
-sphinx-rtd-theme==2.0.0rc2 ; python_version >= "3.7" and python_version < "3.12"
+sphinx-rtd-theme==1.3.0 ; python_version >= "3.7" and python_version < "3.12"
 sphinx==5.3.0 ; python_version >= "3.7" and python_version < "3.12"
 sphinxcontrib-applehelp==1.0.2 ; python_version >= "3.7" and python_version < "3.12"
 sphinxcontrib-devhelp==1.0.2 ; python_version >= "3.7" and python_version < "3.12"

lib/galaxy/dependencies/pinned-requirements.txt

@@ -58,7 +58,7 @@ deprecation==2.1.0 ; python_version >= "3.7" and python_version < "3.12"
 dictobj==0.4 ; python_version >= "3.7" and python_version < "3.12"
 dnspython==2.3.0 ; python_version >= "3.7" and python_version < "3.12"
 docopt==0.6.2 ; python_version >= "3.7" and python_version < "3.12"
-docutils==0.19 ; python_version >= "3.7" and python_version < "3.12"
+docutils==0.18.1 ; python_version >= "3.7" and python_version < "3.12"
 dparse==0.6.3 ; python_version >= "3.7" and python_version < "3.12"
 ecdsa==0.18.0 ; python_version >= "3.7" and python_version < "3.12"
 edam-ontology==1.25.2 ; python_version >= "3.7" and python_version < "3.12"

pyproject.toml

@@ -152,7 +152,7 @@ responses = "*"
 selenium = "*"
 seletools = "*"
 Sphinx = ">=4.0"  # support docutils 0.17
-sphinx_rtd_theme = ">=1.0.0"
+sphinx-rtd-theme = ">=1.0.0,<2"  # https://github.com/python-poetry/poetry/issues/8194
 statsd = "*"
 testfixtures = "*"
 tuspy = "*"