Use _decimal_ literals for the CivilDay example.

Using `07` is a neat pun, but it not friendly to the reader. If the reader naively copies it and then changes the `7` to an `8` or a `9`, it will fail compilation: `invalid digit ... in octal constant`. Best avoided. Note that the other examples do not use octal literals.

PiperOrigin-RevId: 621335289
Change-Id: I6b11a639c5ba675eb29467baf45996ceff0ed9bf

absl/time/civil_time.h

@@ -55,7 +55,7 @@
 // Example:
 //
 //   // Construct a civil-time object for a specific day
-//   const absl::CivilDay cd(1969, 07, 20);
+//   const absl::CivilDay cd(1969, 7, 20);
 //
 //   // Construct a civil-time object for a specific second
 //   const absl::CivilSecond cd(2018, 8, 1, 12, 0, 1);
@@ -65,7 +65,7 @@
 // Example:
 //
 //   // Valid in C++14
-//   constexpr absl::CivilDay cd(1969, 07, 20);
+//   constexpr absl::CivilDay cd(1969, 7, 20);
 
 #ifndef ABSL_TIME_CIVIL_TIME_H_
 #define ABSL_TIME_CIVIL_TIME_H_