Update regex for opertn and opdate

Add `$` to `opertn_NN` and `opdate_NN` regex to avoid conflicts with any future derived columns based on these that may have similar names.

avoidable_admissions/data/validate.py

@@ -126,12 +126,12 @@ class Config:
                 # Modified from https://medium.com/@manabu.torii/regex-pattern-for-icd-10-cm-codes-5763bd66e26d and includes string match for 'nan'
                 checks=pa.Check.str_matches(r'^(?i:[A-Z][0-9][0-9AB](?:[0-9A-KXZ](?:[0-9A-EXYZ](?:[0-9A-HX][0-59A-HJKMNP-S]?)?)?)?|^\bnan\b$)$')
             ),
-            "opertn_[0-9]{2}": pa.Column(
+            "opertn_[0-9]{2}$": pa.Column(
                 str,
                 nullable=True,
                 regex=True,
             ),
-            "opdate_[0-9]{2}": pa.Column(
+            "opdate_[0-9]{2}$": pa.Column(
                 datetime,
                 nullable=True,
                 regex=True,