Fix user guide system overview so nodes don't overlap. (#3307)

* Fix user guide system overview so nodes don't overlap.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

docs/img/overview.mermaidjs

@@ -1,5 +1,5 @@
 stateDiagram-v2
-%%{init:{'state':{'nodeSpacing': 0, 'rankSpacing': 20}}}%%
+%%{init:{'state':{'nodeSpacing': 250, 'rankSpacing': 30}}}%%
 
 [*] --> conf
 conf --> tox_env
@@ -31,7 +31,7 @@ report --> report :for each tox environment
 report --> [*]
 
 conf: build configuration (CLI + files) <br> identify environments to run
-create: create an isolated tox environment <br> the other steps executed within this
+create: create an isolated tox environment <br> the other steps are executed within this
 deps: install project dependencies (if has deps)
 package: build package
 install: install package without dependencies