docs: gcov: replace links with HTTPS

Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.

Deterministic algorithm:
For each file:
  If not .svg:
    For each line:
      If doesn't contain `\bxmlns\b`:
        For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`:
	  If neither `\bgnu\.org/license`, nor `\bmozilla\.org/MPL\b`:
            If both the HTTP and HTTPS versions
            return 200 OK and serve the same content:
              Replace HTTP with HTTPS.
Signed-off-by: Alexander A. Klimov <grandmaster@al2klimov.de>
Link: https://lore.kernel.org/r/20200708161839.15170-1-grandmaster@al2klimov.deSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/dev-tools/gcov.rst

@@ -22,7 +22,7 @@ Possible uses:
 * minimizing kernel configurations (do I need this option if the
   associated code is never run?)
 
-.. _gcov: http://gcc.gnu.org/onlinedocs/gcc/Gcov.html
+.. _gcov: https://gcc.gnu.org/onlinedocs/gcc/Gcov.html
 .. _lcov: http://ltp.sourceforge.net/coverage/lcov.php
 
 
@@ -171,7 +171,7 @@ Note on compilers
 GCC and LLVM gcov tools are not necessarily compatible. Use gcov_ to work with
 GCC-generated .gcno and .gcda files, and use llvm-cov_ for Clang.
 
-.. _gcov: http://gcc.gnu.org/onlinedocs/gcc/Gcov.html
+.. _gcov: https://gcc.gnu.org/onlinedocs/gcc/Gcov.html
 .. _llvm-cov: https://llvm.org/docs/CommandGuide/llvm-cov.html
 
 Build differences between GCC and Clang gcov are handled by Kconfig. It