feat: allow setting c-o-m in exp label (#433)

* Update label.py

Remove hard-coded lumi for loc==4

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

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

* Update label.py

Correctly format com and lumi

* fix: fix tests

---------

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

src/mplhep/label.py

@@ -403,11 +403,19 @@ def exp_label(
             _com_label = r"\mathrm{13\ TeV}"
 
         if lumi is not None:
-            _lumi = (
-                r"$\sqrt{s} = " + _com_label + ", " + str(lumi) + r"\ \mathrm{fb}^{-1}$"
+            _lumi = r"{com}, {lumi}".format(
+                com=r"$\sqrt{s} = \mathrm{" + str(com) + r"\ TeV}$"
+                if com is not None
+                else r"$\sqrt{s} = \mathrm{13\ TeV}$",
+                lumi=lumi_format.format(lumi) + r" $\mathrm{fb^{-1}}$",
             )
         else:
-            _lumi = r"$\sqrt{s} = " + _com_label + "$"
+            _lumi = r"{com}".format(
+                com=r"$\sqrt{s} = \mathrm{" + str(com) + r"\ TeV}$"
+                if com is not None
+                else r"$\sqrt{s} = \mathrm{13\ TeV}$",
+            )
+
         explumi = ExpSuffix(
             *exptext.get_position(),
             text=rlabel if rlabel is not None else _lumi,