Fix a small typo in the survival analysis notebook (#528)

* fix typo in survival function

* run pre-commit

---------

Co-authored-by: Oriol (ZBook) <oriol.abril.pla@gmail.com>

Author: manuelhaussmann

examples/survival_analysis/survival_analysis.ipynb

@@ -209,7 +209,7 @@
     "\n",
     "Solving this differential equation for the survival function shows that\n",
     "\n",
-    "$$S(t) = \\exp\\left(-\\int_0^s \\lambda(s)\\ ds\\right).$$\n",
+    "$$S(t) = \\exp\\left(-\\int_0^t \\lambda(s)\\ ds\\right).$$\n",
     "\n",
     "This representation of the survival function shows that the cumulative hazard function\n",
     "\n",

examples/survival_analysis/survival_analysis.myst.md

@@ -87,7 +87,7 @@ $$\begin{align*}
 
 Solving this differential equation for the survival function shows that
 
-$$S(t) = \exp\left(-\int_0^s \lambda(s)\ ds\right).$$
+$$S(t) = \exp\left(-\int_0^t \lambda(s)\ ds\right).$$
 
 This representation of the survival function shows that the cumulative hazard function