doc(Tactic/MinImports): tidy backticks (#31861)

Found and fixed with help from Codex.

This is the last remaining true positive finding of the detection script in #31463.

Author: harahu

Mathlib/Tactic/MinImports.lean

@@ -113,7 +113,7 @@ def getAttrNames (stx : Syntax) : NameSet :=
     | some stx => getIds stx
 
 /-- `getAttrs env stx` returns all attribute declaration names contained in `stx` and registered
-in the `Environment `env`. -/
+in the `Environment` `env`. -/
 def getAttrs (env : Environment) (stx : Syntax) : NameSet :=
   Id.run do
   let mut new : NameSet := {}