Remove cause of "whitespace in literal operator" warning in Clang 20

[striezel]

When string-view lite is compiled with Clang 20, it emits the following deprecation warnings:

/__w/string-view-lite/string-view-lite/include/nonstd/string_view.hpp:1539:57: warning: identifier '_sv' preceded by whitespace in a literal operator declaration is deprecated [-Wdeprecated-literal-operator]
 1539 | nssv_constexpr nonstd::sv_lite::string_view operator "" _sv( const char* str, size_t len ) nssv_noexcept  // (1)
      |                                             ~~~~~~~~~~~~^~~
      |                                             operator""_sv
/__w/string-view-lite/string-view-lite/include/nonstd/string_view.hpp:1544:60: warning: identifier '_sv' preceded by whitespace in a literal operator declaration is deprecated [-Wdeprecated-literal-operator]
 1544 | nssv_constexpr nonstd::sv_lite::u16string_view operator "" _sv( const char16_t* str, size_t len ) nssv_noexcept  // (2)
      |                                                ~~~~~~~~~~~~^~~
      |                                                operator""_sv
/__w/string-view-lite/string-view-lite/include/nonstd/string_view.hpp:1549:60: warning: identifier '_sv' preceded by whitespace in a literal operator declaration is deprecated [-Wdeprecated-literal-operator]
 1549 | nssv_constexpr nonstd::sv_lite::u32string_view operator "" _sv( const char32_t* str, size_t len ) nssv_noexcept  // (3)
      |                                                ~~~~~~~~~~~~^~~
      |                                                operator""_sv
/__w/string-view-lite/string-view-lite/include/nonstd/string_view.hpp:1554:58: warning: identifier '_sv' preceded by whitespace in a literal operator declaration is deprecated [-Wdeprecated-literal-operator]
 1554 | nssv_constexpr nonstd::sv_lite::wstring_view operator "" _sv( const wchar_t* str, size_t len ) nssv_noexcept  // (4)
      |                                              ~~~~~~~~~~~~^~~
      |                                              operator""_sv

An example of that can be seen in this workflow run in the "Build tests" step.

To fix that problem the space characters in the literal operator declarations are removed.