Fix trailing whitespace in code literal

rst apparently requires that the closing double backticks for code literals
appear at the end of a "word", rather than preceded by a space as markdown
allows. This means that ``` ``julia> `` ``` doesn't parse correctly. The
fix is to just remove the trailing space and explicitly mention the need
for a space after the `>`.

doc/manual/interacting-with-julia.rst

@@ -42,8 +42,8 @@ There are a number useful features unique to interactive work. In addition to sh
     julia> ans
     "12"
 
-In Julia mode, the REPL supports something called *prompt pasting*. This activates when pasting text that starts with ``julia> `` into the REPL.
-In that case, only expressions starting with ``julia> `` are parsed, others are removed.
+In Julia mode, the REPL supports something called *prompt pasting*. This activates when pasting text that starts with ``julia>`` (with a single space after ``>``) into the REPL.
+In that case, only expressions starting with ``julia>`` are parsed, others are removed.
 This makes it is possible to paste a chunk of code that has been copied from a REPL session without having to scrub away prompts and outputs.
 This feature is enabled by default but can be disabled or enabled at will with ``Base.REPL.enable_promptpaste(::Bool)``.
 If it is enabled, you can try it out by pasting the code block above this paragraph straight into the REPL.