Remove redundant test.

The condition "context_start < context_end" is strictly weaker
than "context_end - context_start >= 50", so we don't need both.
Oversight in commit ffd3944ab, noted by tanghy.fnst.

In passing, line-wrap a nearby test to make it more readable.

Discussion: https://postgr.es/m/OS0PR01MB61137C4054774F44E3A9DC89FBC69@OS0PR01MB6113.jpnprd01.prod.outlook.com

src/backend/utils/adt/jsonfuncs.c

@@ -652,7 +652,7 @@ report_json_context(JsonLexContext *lex)
 	context_end = lex->token_terminator;
 
 	/* Advance until we are close enough to context_end */
-	while (context_end - context_start >= 50 && context_start < context_end)
+	while (context_end - context_start >= 50)
 	{
 		/* Advance to next multibyte character */
 		if (IS_HIGHBIT_SET(*context_start))
@@ -680,7 +680,9 @@ report_json_context(JsonLexContext *lex)
 	 * suffixing "..." if not ending at end of line.
 	 */
 	prefix = (context_start > line_start) ? "..." : "";
-	suffix = (lex->token_type != JSON_TOKEN_END && context_end - lex->input < lex->input_length && *context_end != '\n' && *context_end != '\r') ? "..." : "";
+	suffix = (lex->token_type != JSON_TOKEN_END &&
+			  context_end - lex->input < lex->input_length &&
+			  *context_end != '\n' && *context_end != '\r') ? "..." : "";
 
 	return errcontext("JSON data, line %d: %s%s%s",
 					  lex->line_number, prefix, ctxt, suffix);