Creates newlines in the %%timeit documentation (#14556)

Fixes  #13873 by adding empty lines after semicolons, rendering blocks
correctly.
Fixes the issue pointed out by this
[comment](https://github.com/ipython/ipython/issues/13873#issuecomment-1363442055)

Fixes unintentional bolding in the later part of the same section, by
removing indentation:

![image](https://github.com/user-attachments/assets/0200ff8a-6a0d-4250-85d6-ddb94c04725c)

IPython/core/magics/execution.py

@@ -195,12 +195,16 class ExecutionMagics(Magics):
 
         """Run a statement through the python code profiler.
 
-        Usage, in line mode:
+        **Usage, in line mode:**
+
           %prun [options] statement
 
-        Usage, in cell mode:
+        **Usage, in cell mode:**
+
           %%prun [options] [statement]
+
           code...
+
           code...
 
         In cell mode, the additional code lines are appended to the (possibly
@@ -1028,11 +1032,16 class ExecutionMagics(Magics):
     def timeit(self, line='', cell=None, local_ns=None):
         """Time execution of a Python statement or expression
 
-        Usage, in line mode:
+        **Usage, in line mode:**
+
           %timeit [-n<N> -r<R> [-t|-c] -q -p<P> -o] statement
-        or in cell mode:
+
+        **or in cell mode:**
+
           %%timeit [-n<N> -r<R> [-t|-c] -q -p<P> -o] setup_code
+
         code
+
         code...
 
         Time execution of a Python statement or expression using the timeit
@@ -1046,6 +1055,7 class ExecutionMagics(Magics):
           body has access to any variables created in the setup code.
 
         Options:
+
         -n<N>: execute the given statement <N> times in a loop. If <N> is not
         provided, <N> is determined so as to get sufficient accuracy.