[tcl/en] Fix typo (#4225)

Removed unnecessary "string".

tcl.html.markdown

@@ -308,7 +308,7 @@ set result [+ 5 3]
 set name Neo
 expr {{Bob} eq $name}
 
-# The general operators fall back to string string comparison if numeric
+# The general operators fall back to string comparison if numeric
 # operation isn't feasible:
 expr {{Bob} == $name}