Fix tiny typo

I think the intent is: https://en.wiktionary.org/wiki/producible

amount.go

@@ -67,7 +67,7 @@ func round(f float64) Amount {
 // NewAmount creates an Amount from a floating point value representing
 // some value in bitcoin.  NewAmount errors if f is NaN or +-Infinity, but
 // does not check that the amount is within the total amount of bitcoin
-// producable as f may not refer to an amount at a single moment in time.
+// producible as f may not refer to an amount at a single moment in time.
 func NewAmount(f float64) (Amount, error) {
 	// The amount is only considered invalid if it cannot be represented
 	// as an integer type.  This may happen if f is NaN or +-Infinity.

amount_test.go

@@ -26,25 +26,25 @@ func TestAmountCreation(t *testing.T) {
 			expected: 0,
 		},
 		{
-			name:     "max producable",
+			name:     "max producible",
 			amount:   21e6,
 			valid:    true,
 			expected: MaxSatoshi,
 		},
 		{
-			name:     "min producable",
+			name:     "min producible",
 			amount:   -21e6,
 			valid:    true,
 			expected: -MaxSatoshi,
 		},
 		{
-			name:     "exceeds max producable",
+			name:     "exceeds max producible",
 			amount:   21e6 + 1e-8,
 			valid:    true,
 			expected: MaxSatoshi + 1,
 		},
 		{
-			name:     "exceeds min producable",
+			name:     "exceeds min producible",
 			amount:   -21e6 - 1e-8,
 			valid:    true,
 			expected: -MaxSatoshi - 1,