fix: undo the accidental revert of #11877 in #11807 (#15523)

A bad merge in #11807 causes the change from #11877 (removing `import ProofWidgets`) to be reverted.

Mathlib/Tactic/Common.lean

@@ -11,11 +11,6 @@ import Qq
 -- Tools for analysing imports, like `#find_home`, `#minimize_imports`, ...
 import ImportGraph.Imports
 
--- Currently we don't need to import all of ProofWidgets,
--- but without this, if you don't run `lake build ProofWidgets` then `make test` will fail.
--- Hopefully `lake` will be able to handle tests later.
-import ProofWidgets
-
 -- Import common Batteries tactics and commands
 import Batteries.Tactic.Where
 

Mathlib/Tactic/Widget/StringDiagram.lean

@@ -4,6 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Yuma Mizuno
 -/
 import ProofWidgets.Component.PenroseDiagram
+import ProofWidgets.Component.Panel.Basic
 import ProofWidgets.Presentation.Expr
 import Mathlib.Tactic.CategoryTheory.Monoidal