[pandas-vet] Deprecate pandas-df-variable-name (PD901) (#18618)

Summary
--

Deprecates PD901 as part of #7710. I don't feel particularly strongly
about this one, though I have certainly used `df` as a dataframe name in
the past, just going through the open issues in the 0.12 milestone.

Test Plan
--

N/a

Author: ntBre

crates/ruff_linter/src/codes.rs

@@ -752,7 +752,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (PandasVet, "013") => (RuleGroup::Stable, rules::pandas_vet::rules::PandasUseOfDotStack),
         (PandasVet, "015") => (RuleGroup::Stable, rules::pandas_vet::rules::PandasUseOfPdMerge),
         (PandasVet, "101") => (RuleGroup::Stable, rules::pandas_vet::rules::PandasNuniqueConstantSeriesCheck),
-        (PandasVet, "901") => (RuleGroup::Stable, rules::pandas_vet::rules::PandasDfVariableName),
+        (PandasVet, "901") => (RuleGroup::Deprecated, rules::pandas_vet::rules::PandasDfVariableName),
 
         // flake8-errmsg
         (Flake8ErrMsg, "101") => (RuleGroup::Stable, rules::flake8_errmsg::rules::RawStringInException),

crates/ruff_linter/src/rules/pandas_vet/rules/assignment_to_df.rs

@@ -4,6 +4,10 @@ use ruff_text_size::Ranged;
 
 use crate::{Violation, checkers::ast::Checker};
 
+/// ## Deprecated
+///
+/// This rule has been deprecated as it's highly opinionated and overly strict in most cases.
+///
 /// ## What it does
 /// Checks for assignments to the variable `df`.
 ///