Fix a handful of typos (#3605)

docs/content/manual/v1.4/manual.yml

@@ -1414,7 +1414,7 @@ sections:
       which to place the data.
 
       It is also possible to define functions in jq, although this is
-      is a feature whose biggest use is defining jq's standard library
+      a feature whose biggest use is defining jq's standard library
       (many jq functions such as `map` and `select` are in fact written
       in jq).