MNT: Use noarch python {{ python_min }} variable

* Use 'python {{ python_min }}' syntax for the python requirements for noarch
  python recipes.
   - c.f. https://conda-forge.org/docs/maintainer/knowledge_base/#noarch-python
* Use a Jinja2 set statement for python_min to keep all the build metadata
  contained in the recipe/meta.yaml and override the global python_min
  with scikit-hep-testdata's python_min of 3.8.
* Remove --no-deps --no-build-isolation 'pip install' options in recipes as
  the build tool (e.g. conda-build, rattler-build) will enforce all required
  'pip install' options itself at build time.
* Bump build number.

recipe/meta.yaml

@@ -1,5 +1,6 @@
 {% set name = "scikit-hep-testdata" %}
 {% set version = "0.5.0" %}
+{% set python_min = "3.8" %}
 
 package:
   name: {{ name|lower }}
@@ -10,18 +11,18 @@ source:
   sha256: 50b7d14d558cd14e8dad4021ae02c3068a29a613be39fbc046fd79c15af56819
 
 build:
-  number: 0
+  number: 1
   noarch: python
-  script: 'SETUPTOOLS_SCM_PRETEND_VERSION={{ version }} {{ PYTHON }} -m pip install . --no-deps --ignore-installed -vv '
+  script: SETUPTOOLS_SCM_PRETEND_VERSION={{ version }} {{ PYTHON }} -m pip install . -vv
 
 requirements:
   host:
     - pip
-    - python >=3.8
+    - python {{ python_min }}
     - setuptools
     - setuptools_scm
   run:
-    - python >=3.8
+    - python >={{ python_min }}
     - pyyaml
     - importlib_resources
     - requests
@@ -30,6 +31,7 @@ test:
   source_files:
     - tests
   requires:
+    - python {{ python_min }}
     - pytest
     - pip
   imports: