docs(rules): remove no longer existing NLP rules (conventional-changelog#2523)

They're not deprecated, but actually removed in v7.3.0, commit
2e7e34d

Author: scop

docs/reference-rules.md

@@ -402,78 +402,3 @@ Infinity
 ```
 'Signed-off-by:'
 ```
-
-### Deprecated rules
-
-#### body-tense `deprecated`
-
-- **condition**: `body` is verbalized in tense present in `value`
-- **rule**: `always`
-- **value**
-
-```
-['present-imperative']
-```
-
-- **possible values**
-
-```
-[
-  'past-tense', // did
-  'present-imperative', // do
-  'present-participle', // doing
-  'present-third-person' // does
-]
-```
-
-#### footer-tense `deprecated`
-
-- **condition**: `footer` is verbalized in tense present in `value`
-- **rule**: `always`
-- **value**
-
-```
-['present-imperative']
-```
-
-- **possible values**
-
-```
-[
-  'past-tense', // did
-  'present-imperative', // do
-  'present-participle', // doing
-  'present-third-person' // does
-]
-```
-
-#### lang `deprecated`
-
-- **condition**: `subject` is of language `value`
-- **rule**: `always`
-- **value**
-
-```
-eng
-```
-
-#### subject-tense `deprecated`
-
-- **condition**: `subject` is verbalized in tense present in `value`
-- **rule**: `always`
-- **value**
-
-```
-['present-imperative']
-```
-
-- **possible values**
-
-```
-[
-  'past-tense', // did
-  'present-imperative', // do
-  'present-participle', // doing
-  'present-third-person' // does
-]
-```