Substituting plain headed box when show_header=False on Table (#2330)

* Substituting plain headed box when show_header=False on Table

* Update changelog

* Revert __main__ in table to remove test code

.pre-commit-config.yaml

@@ -14,7 +14,6 @@ repos:
       - id: check-yaml
       - id: end-of-file-fixer
       - id: mixed-line-ending
-      - id: trailing-whitespace
       - id: check-vcs-permalinks
       - id: check-shebang-scripts-are-executable
   - repo: https://github.com/pre-commit/pygrep-hooks
@@ -31,7 +30,7 @@ repos:
       - id: pycln
         args: [--all]
   - repo: https://github.com/psf/black
-    rev: 22.1.0
+    rev: 22.3.0
     hooks:
       - id: black
         exclude: ^benchmarks/

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix text wrapping edge case https://github.com/Textualize/rich/pull/2296
 - Allow exceptions that are raised while a Live is rendered to be displayed and/or processed https://github.com/Textualize/rich/pull/2305
 - Fix crashes that can happen with `inspect` when docstrings contain some special control codes https://github.com/Textualize/rich/pull/2294
+- Fix edges used in first row of tables when `show_header=False` https://github.com/Textualize/rich/pull/2330
 
 ## [12.4.4] - 2022-05-24