Revert "std.fmt: require specifier for unwrapping ?T and E!T."

This reverts commit 7cbd586ace46a8e8cebab660ebca3cfc049305d9.

This is causing a fail to build from source:

```
./lib/std/fmt.zig:492:17: error: cannot format optional without a specifier (i.e. {?} or {any})
                @compileError("cannot format optional without a specifier (i.e. {?} or {any})");
                ^
./src/link/MachO/Atom.zig:544:26: note: called from here
                log.debug("  RELA({s}) @ {x} => %{d} in object({d})", .{
                         ^
```

I looked at the code to fix it but none of those args are optionals.

1 files changed, 4 insertions, 4 deletions

diff --git a/doc/langref.html.in b/doc/langref.html.in
index 81ccd58261..13c7da4a8a 100644
--- a/doc/langref.html.in
+++ b/doc/langref.html.in
@@ -574,7 +574,7 @@ pub fn main() void {
     var optional_value: ?[]const u8 = null;
     assert(optional_value == null);
 
-    print("\noptional 1\ntype: {s}\nvalue: {?s}\n", .{
+    print("\noptional 1\ntype: {s}\nvalue: {s}\n", .{
         @typeName(@TypeOf(optional_value)),
         optional_value,
     });
@@ -582,7 +582,7 @@ pub fn main() void {
     optional_value = "hi";
     assert(optional_value != null);
 
-    print("\noptional 2\ntype: {s}\nvalue: {?s}\n", .{
+    print("\noptional 2\ntype: {s}\nvalue: {s}\n", .{
         @typeName(@TypeOf(optional_value)),
         optional_value,
     });
@@ -590,14 +590,14 @@ pub fn main() void {
     // error union
     var number_or_error: anyerror!i32 = error.ArgNotFound;
 
-    print("\nerror union 1\ntype: {s}\nvalue: {!}\n", .{
+    print("\nerror union 1\ntype: {s}\nvalue: {}\n", .{
         @typeName(@TypeOf(number_or_error)),
         number_or_error,
     });
 
     number_or_error = 1234;
 
-    print("\nerror union 2\ntype: {s}\nvalue: {!}\n", .{
+    print("\nerror union 2\ntype: {s}\nvalue: {}\n", .{
         @typeName(@TypeOf(number_or_error)),
         number_or_error,
     });