[flang] Fix build break after bac9575

.../flang/lib/Optimizer/Builder/FIRBuilder.cpp: In function ‘llvm::Small
Vector<mlir::Value> fir::factory::updateRuntimeExtentsForEmptyArrays(fir
::FirOpBuilder&, mlir::Location, mlir::ValueRange)’:
.../flang/lib/Optimizer/Builder/FIRBuilder.cpp:1786:10: error: could not
 convert ‘newExtents’ from ‘SmallVector<[...],15>’ to ‘SmallVector<[...]
,6>’
 1786 |   return newExtents;
      |          ^~~~~~~~~~
      |          |
      |          SmallVector<[...],15>

Remove size from template parameters in the declaration of `newExtents`.

Author: kparzysz

flang/lib/Optimizer/Builder/FIRBuilder.cpp

@@ -1778,7 +1778,7 @@ llvm::SmallVector<mlir::Value> fir::factory::updateRuntimeExtentsForEmptyArrays(
     isEmpty = builder.create<mlir::arith::OrIOp>(loc, isEmpty, isZero);
   }
 
-  llvm::SmallVector<mlir::Value, Fortran::common::maxRank> newExtents;
+  llvm::SmallVector<mlir::Value> newExtents;
   for (auto [zero, extent] : llvm::zip_equal(zeroes, extents)) {
     newExtents.push_back(
         builder.create<mlir::arith::SelectOp>(loc, isEmpty, zero, extent));