Clarify default value for OTEL_EXPORTER_OTLP_TIMEOUT to include units (seconds)

Author: ta-ke-inf

opentelemetry-sdk/src/opentelemetry/sdk/environment_variables/__init__.py

@@ -335,7 +335,7 @@
 .. envvar:: OTEL_EXPORTER_OTLP_TIMEOUT
 
 The :envvar:`OTEL_EXPORTER_OTLP_TIMEOUT` is the maximum time the OTLP exporter will wait for each batch export.
-Default: 10
+Default: 10 (seconds)
 """
 
 OTEL_EXPORTER_OTLP_ENDPOINT = "OTEL_EXPORTER_OTLP_ENDPOINT"