[clang][analyzer][NFC] Change PlacementNewChecker into PlacementNew in documentation

[PiotrZSL]

Summary

Check name according to Checkers.td is actually a PlacementNew.

[PiotrZSL]

Micro fix ("" characters).

[steakhal]

Correct. Thanks.

[steakhal]

Do we have other typos like this?

[PiotrZSL]

In D157702#4580310, @steakhal wrote:

Do we have other typos like this?

I don't think so, only mess in overall documentation: https://github.com/llvm/llvm-project/issues/64614
I updated gen-static-analyzer-docs.py, and it shown me that some documentation is missing: https://clang.llvm.org/extra/clang-tidy/checks/list.html.
You can see it, as there are no links for some checks.

[steakhal]

In D157702#4580384, @PiotrZSL wrote:

In D157702#4580310, @steakhal wrote:

Do we have other typos like this?

I don't think so, only mess in overall documentation: https://github.com/llvm/llvm-project/issues/64614
I updated gen-static-analyzer-docs.py, and it shown me that some documentation is missing: https://clang.llvm.org/extra/clang-tidy/checks/list.html.
You can see it, as there are no links for some checks.

Yea, it's a complete mess, I agree.
I have no stakes on the docs, but I know that Ericsson folks do. They might wanna chim in. @donat.nagy @Szelethus

clang/docs/analyzer/checkers.rst

 Check for memory leaks. Traces memory managed by new/delete.
 
 .. code-block:: cpp
 
  void test() {
    int *p = new int;
  } // warn
 
-.. _cplusplus-PlacementNewChecker:
+.. _cplusplus-PlacementNew:
 
-cplusplus.PlacementNewChecker (C++)
-"""""""""""""""""""""""""""""""""""
+cplusplus.PlacementNew (C++)
+""""""""""""""""""""""""""""
 Check if default placement new is provided with pointers to sufficient storage capacity.
 
 .. code-block:: cpp
 
  #include <new>
 
  void f() {
    short s;