Update elements.jl

Typo in Bromine density

Author: Eben60

src/elements.jl

@@ -716,7 +716,7 @@ const _elements_data = [
             boil=332.0K,
             category="diatomic nonmetal",
             cpk_hex="#a62929",
-            density=23.1028g/cm^3,
+            density=3.1028g/cm^3,
             discovered_by="Antoine Jérôme Balard",
             el_config="1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁵",
             melt=265.8K,