refactor: Change namespace of SL2C

HepLean/Lorentz/SL2C/Basic.lean

@@ -15,7 +15,7 @@ import HepLean.Meta.Informal
 The aim of this file is to give the relationship between `SL(2, ℂ)` and the Lorentz group.
 
 -/
-namespace SpaceTime
+namespace Lorentz
 
 open Matrix
 open MatrixGroups
@@ -23,8 +23,6 @@ open Complex
 
 namespace SL2C
 
-open SpaceTime
-
 noncomputable section
 
 /-!
@@ -189,4 +187,4 @@ informal_lemma toRestrictedLorentzGroup where
 end
 end SL2C
 
-end SpaceTime
+end Lorentz