[lldb][docs] Fix plaintext markers in command map

Single backticks RST tries to resolve to a reference.
Double means plaintext.

Fixes these warnings:
map.rst:803: WARNING: 'any' reference target not found: target.prefer-dynamic-value
map.rst:814: WARNING: 'any' reference target not found: expr

Author: DavidSpickett

lldb/docs/use/map.rst

@@ -802,7 +802,7 @@ Print the dynamic type of the result of an expression
 
 LLDB does this automatically if determining the dynamic type does not require
 running the target (in C++, running the target is never needed). This default is
-controlled by the `target.prefer-dynamic-value` setting. If that is disabled, it
+controlled by the ``target.prefer-dynamic-value`` setting. If that is disabled, it
 can be re-enabled on a per-command basis:
 
 .. code-block:: shell
@@ -812,7 +812,7 @@ can be re-enabled on a per-command basis:
   (lldb) expr -d no-run-target -- someCPPObjectPtr
 
 Note that printing of the dynamic type of references is not possible with the
-`expr` command. The workaround is to take the address of the reference and
+``expr`` command. The workaround is to take the address of the reference and
 instruct lldb to print the children of the resulting pointer.
 
 .. code-block:: shell