common: remove spaces before literal operator

clang 20 complains when compiling a user-defined literal operator
with spaces before the underscore. so let's drop the space to be
compliant to
[CWG2521](https://cplusplus.github.io/CWG/issues/2521.html).

```
/home/kefu/dev/ceph/src/common/options.h:415:41: warning: identifier '_min' preceded by whitespace in a literal operator declaration is deprecated [-Wdeprecated-literal-operator]
  415 | constexpr unsigned long long operator"" _min (unsigned long long min) {
      |                              ~~~~~~~~~~~^~~~
      |                              operator""_min
```

Signed-off-by: Kefu Chai <[email protected]>

Author: tchaikov

src/common/options.h

@@ -412,25 +412,25 @@ struct Option {
   }
 };
 
-constexpr unsigned long long operator"" _min (unsigned long long min) {
+constexpr unsigned long long operator""_min (unsigned long long min) {
   return min * 60;
 }
-constexpr unsigned long long operator"" _hr (unsigned long long hr) {
+constexpr unsigned long long operator""_hr (unsigned long long hr) {
   return hr * 60 * 60;
 }
-constexpr unsigned long long operator"" _day (unsigned long long day) {
+constexpr unsigned long long operator""_day (unsigned long long day) {
   return day * 24 * 60 * 60;
 }
-constexpr unsigned long long operator"" _K (unsigned long long n) {
+constexpr unsigned long long operator""_K (unsigned long long n) {
   return n << 10;
 }
-constexpr unsigned long long operator"" _M (unsigned long long n) {
+constexpr unsigned long long operator""_M (unsigned long long n) {
   return n << 20;
 }
-constexpr unsigned long long operator"" _G (unsigned long long n) {
+constexpr unsigned long long operator""_G (unsigned long long n) {
   return n << 30;
 }
-constexpr unsigned long long operator"" _T (unsigned long long n) {
+constexpr unsigned long long operator""_T (unsigned long long n) {
   return n << 40;
 }