Remove unused field NaturalLanguageDomain.location_constraint_regex.

It was documented as "please do not use" and never implemented.

PiperOrigin-RevId: 621881996

RELEASE.md

@@ -16,6 +16,9 @@
 
 ## Breaking Changes
 
+*   Removed `NaturalLanguageDomain.location_constraint_regex`.
+    It was documented as "please do not use" and never implemented.
+
 ## Deprecations
 
 *   Deprecated Python 3.8 support.

tensorflow_metadata/proto/v0/schema.proto

@@ -620,21 +620,7 @@ message NaturalLanguageDomain {
   repeated SequenceValueConstraints token_constraints = 3;
   optional SequenceLengthConstraints sequence_length_constraints = 5;
 
-  // Specifies the location constraints as a function of the tokens specified
-  // in token_constraints.
-  //
-  // String tokens will be specified by S_TOKEN_, (e.g. S_(PAD)_) and integer
-  // tokens will be specified as I_#_ (e.g. I_123_).
-  // A_T_ will match any token that has not been specified in token_constraints.
-  // Parenthesis, +, and * are supported.
-  // _ will be escapable with a \ for tokens containing it (e.g. FOO\_BAR).
-  //
-  // For example, a two-sequence BERT model may look as follows:
-  // S_(CLS)_ A_T_+ S_(SEP)_ A_T_+ S_(SEP)_ S_(PAD)_*
-  //
-  // Note: Support for this field is not yet implemented. Please do not use.
-  // TODO(b/188095987): Remove warning once field is implemented.
-  optional string location_constraint_regex = 4;
+  reserved 4;
 }
 
 // Image data.