Fix inconsistent equalfuncs.c behavior for FuncCall.funcformat.

Other equalfuncs.c checks on CoercionForm fields use
COMPARE_COERCIONFORM_FIELD (which makes them no-ops),
but commit 40c24bfef neglected to make _equalFuncCall
do likewise.  Fix that.

This is only strictly correct if FuncCall.funcformat has
no semantic effect, instead just determining ruleutils.c
display formatting.  40c24bfef added a couple of checks
in parse analysis that could break that rule; but on closer
inspection, they're redundant, so just take them out again.

Per report from Noah Misch.

Discussion: https://postgr.es/m/20210606063331.GC297923@rfd.leadboat.com

src/backend/parser/parse_clause.c

@@ -543,7 +543,6 @@ transformRangeFunction(ParseState *pstate, RangeFunction *r)
 				!fc->agg_star &&
 				!fc->agg_distinct &&
 				!fc->func_variadic &&
-				fc->funcformat == COERCE_EXPLICIT_CALL &&
 				coldeflist == NIL)
 			{
 				ListCell   *lc;