fix "\" appearing in the rendered docs preview in the post_treatment term of the banking dataset notebook

Author: mercury0100

docs/source/notebooks/did_pymc_banks.ipynb

@@ -838,7 +838,7 @@
     "\\mu_i &= \\gamma && \\color{#FA8072}{\\text{(global intercept)}} \\\\\n",
     "&+ \\alpha[\\text{district}_i] && \\color{#FA8072}{\\text{(unit fixed effect)}} \\\\\n",
     "&+ \\beta[\\text{year}_i] && \\color{#FA8072}{\\text{(time fixed effect)}} \\\\\n",
-    "&+ \\Delta \\cdot \\text{district}_i \\cdot \\text{post\\_treatment}_i && \\color{#FA8072}{\\text{(treatment indicator)}}\n",
+    "&+ \\Delta \\cdot \\text{district}_i \\cdot \\text{post_treatment}_i && \\color{#FA8072}{\\text{(treatment indicator)}}\n",
     "\\end{aligned}\n",
     "$$\n",
     "\n",