readme: typo

README.md

@@ -212,7 +212,7 @@ If you want more precision, just set the
 | Variable | Default Value | Description |
 |----------|---------------|-------------|
 |`POWERLEVEL9K_COMMAND_EXECUTION_TIME_THRESHOLD`|3|Threshold above which to print this segment. Can be set to `0` to always print.|
-|`POWERLEVEL9K_COMMAND_EXECUTION_TIME_PRECISION=2`|2|Number of digits to use in the fractional part of the time value.|
+|`POWERLEVEL9K_COMMAND_EXECUTION_TIME_PRECISION`|2|Number of digits to use in the fractional part of the time value.|
 
 ##### custom_command