Merge pull request micropython#8685 from jepler/document-monotonic-better

Document that the "monotonic" values are only monotonic in one code run

Author: tannewt

shared-bindings/time/__init__.c

@@ -42,7 +42,8 @@
 //|
 //| def monotonic() -> float:
 //|     """Returns an always increasing value of time with an unknown reference
-//|     point. Only use it to compare against other values from `time.monotonic()`.
+//|     point. Only use it to compare against other values from `time.monotonic()`
+//|     during the same code run.
 //|
 //|     On most boards, `time.monotonic()` converts a 64-bit millisecond tick counter
 //|     to a float. Floats on most boards are encoded in 30 bits internally, with
@@ -212,6 +213,8 @@ MP_DEFINE_CONST_FUN_OBJ_0(time_time_obj, time_time);
 //| def monotonic_ns() -> int:
 //|     """Return the time of the monotonic clock, which cannot go backward, in nanoseconds.
 //|     Not available on boards without long integer support.
+//|     Only use it to compare against other values from `time.monotonic()`
+//|     during a single code run.
 //|
 //|     :return: the current time
 //|     :rtype: int"""