tests: Don't install docs dependencies on Python 3.8 or 3.13

Some of them are not ready for Python 3.13 (and latest Pandas doesn't support Python 3.8), and therefore prevent installing the rest of the dependencies for this Python version, in turn preventing us to run tests on Python 3.13 locally.

devdeps.txt

@@ -31,19 +31,19 @@ mkdocstrings[python]>=0.25
 tomli>=2.0; python_version < '3.11'
 
 # docs gallery
-pydeps>=1.12
-diagrams>=0.21
-rich>=12.3
-matplotlib>=3.5
-numpy>=1.24.4
-textual>=0.67
-pytermgui>=6.3
-pipdeptree>=2.6
-pip>=24
-pygments>=2.15
-drawsvg>=2.3
-hyperbolic>=2.0
-qrcode>=7.4
-plotly>=5.22
-pandas>=2.2
-chalk-diagrams>=0.2
+pydeps>=1.12; python_version > '3.8' and python_version < '3.13'
+diagrams>=0.21; python_version > '3.8' and python_version < '3.13'
+rich>=12.3; python_version > '3.8' and python_version < '3.13'
+matplotlib>=3.5; python_version > '3.8' and python_version < '3.13'
+numpy>=1.24.4; python_version > '3.8' and python_version < '3.13'
+textual>=0.67; python_version > '3.8' and python_version < '3.13'
+pytermgui>=6.3; python_version > '3.8' and python_version < '3.13'
+pipdeptree>=2.6; python_version > '3.8' and python_version < '3.13'
+pip>=24; python_version > '3.8' and python_version < '3.13'
+pygments>=2.15; python_version > '3.8' and python_version < '3.13'
+drawsvg>=2.3; python_version > '3.8' and python_version < '3.13'
+hyperbolic>=2.0; python_version > '3.8' and python_version < '3.13'
+qrcode>=7.4; python_version > '3.8' and python_version < '3.13'
+plotly>=5.22; python_version > '3.8' and python_version < '3.13'
+pandas>=2.2; python_version > '3.8' and python_version < '3.13'
+chalk-diagrams>=0.2; python_version > '3.8' and python_version < '3.13'