Fix heading format for 'date' section in README

Author: jlanzarotta

README.adoc

@@ -414,7 +414,7 @@ Enter Date Time (empty for no change) [2024-04-10T10:32:24-04:00] : 2024-04-10T1
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-=== date
+==== date
 
 Using this option, you are shown a list of all the entries for specified date. The date *MUST* be in `YYYY-MM-DD` format.  You are then given the opportunity to choose the entry you would like to amend, just like when specifying `today`.