Regenerate UCUM and FHIRPath lexers/parsers with latest antlr4

And update to 4.9.3.

I also removed the generated tokens and interp files as those are not
needed at runtime (source:
https://stackoverflow.com/questions/59734259/antlr-generated-files).

Commands for regenerating:
```
antlr4 -no-listener -package com.ibm.fhir.model.ucum fhir-model/UCUM.g4
&& sed -i.bak $'s/\t/    /g' fhir-model/UCUM*.java && mv
fhir-model/UCUM*.java fhir-model/src/main/java/com/ibm/fhir/model/ucum/
```
```
antlr4 -visitor -no-listener -package com.ibm.fhir.path fhir-path/FHIRPath.g4 &&
sed -i.bak $'s/\t/    /g' fhir-path/FHIRPath*.java && mv
fhir-path/FHIRPath*.java fhir-path/src/main/java/com/ibm/fhir/path/
```

Signed-off-by: Lee Surprenant <lmsurpre@us.ibm.com>

fhir-model/src/main/java/com/ibm/fhir/model/ucum/UCUMLexer.java

@@ -1,12 +1,11 @@
 /*
- * (C) Copyright IBM Corp. 2020, 2021
+ * (C) Copyright IBM Corp. 2021
  *
  * SPDX-License-Identifier: Apache-2.0
  */
 
-// Generated from UCUM.g4 by ANTLR 4.9.1
+// Generated from fhir-model/UCUM.g4 by ANTLR 4.9.3
 package com.ibm.fhir.model.ucum;
-
 import org.antlr.v4.runtime.CharStream;
 import org.antlr.v4.runtime.Lexer;
 import org.antlr.v4.runtime.RuntimeMetaData;
@@ -20,7 +19,7 @@
 
 @SuppressWarnings({"all", "warnings", "unchecked", "unused", "cast"})
 public class UCUMLexer extends Lexer {
-    static { RuntimeMetaData.checkVersion("4.9.1", RuntimeMetaData.VERSION); }
+    static { RuntimeMetaData.checkVersion("4.9.3", RuntimeMetaData.VERSION); }
 
     protected static final DFA[] _decisionToDFA;
     protected static final PredictionContextCache _sharedContextCache =

fhir-model/src/main/java/com/ibm/fhir/model/ucum/UCUMParser.java

@@ -1,12 +1,11 @@
 /*
- * (C) Copyright IBM Corp. 2020, 2021
+ * (C) Copyright IBM Corp. 2021
  *
  * SPDX-License-Identifier: Apache-2.0
  */
 
-// Generated from UCUM.g4 by ANTLR 4.9.1
+// Generated from fhir-model/UCUM.g4 by ANTLR 4.9.3
 package com.ibm.fhir.model.ucum;
-
 import java.util.List;
 
 import org.antlr.v4.runtime.NoViableAltException;
@@ -27,7 +26,7 @@
 
 @SuppressWarnings({"all", "warnings", "unchecked", "unused", "cast"})
 public class UCUMParser extends Parser {
-    static { RuntimeMetaData.checkVersion("4.9.1", RuntimeMetaData.VERSION); }
+    static { RuntimeMetaData.checkVersion("4.9.3", RuntimeMetaData.VERSION); }
 
     protected static final DFA[] _decisionToDFA;
     protected static final PredictionContextCache _sharedContextCache =

fhir-parent/pom.xml

@@ -402,7 +402,7 @@
             <dependency>
                 <groupId>org.antlr</groupId>
                 <artifactId>antlr4-runtime</artifactId>
-                <version>4.9.1</version>
+                <version>4.9.3</version>
             </dependency>
             <dependency>
                 <groupId>jakarta.mail</groupId>