swapin: Fixed the spelling mistake of funciton to function

[nagarevaibhav]

Previously man page:

DESCRIPTION
       This  tool  counts  swapins by process, to show which process is affected by swapping (if swap de‐
       vices are in use). This can explain a significant source of application latency, if it  has  began
       swapping due to memory pressure on the system.

       This works by tracing the swap_readpage() kernel funciton using dynamic instrumentation. This tool
       may need maintenance to keep working if that function changes in later kernels.

       Since this uses BPF, only the root user can use this tool.

Now:

DESCRIPTION
       This  tool  counts  swapins by process, to show which process is affected by swapping (if swap de‐
       vices are in use). This can explain a significant source of application latency, if it  has  began
       swapping due to memory pressure on the system.

       This works by tracing the swap_readpage() kernel function using dynamic instrumentation. This tool
       may need maintenance to keep working if that function changes in later kernels.

       Since this uses BPF, only the root user can use this tool.